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The latest on high definition TV $3.50 JANUARY 1990 NZ S4.95 ~~CTL \~~~~-s Up to 99% of our s products are in stock! Other companies might have similar products . . . but! Q: Do they have the products in stock? A: Aaahh - due in next week/month/year! Q: Do they give you a 14 day money-back guarantee? A: A what? Q: Do they give you after-sales service? A: What's a service? Q: Do they despatch the goods within 24hours (usually less?) ALL-IN-ONE MOTHERBOARD BARGAIN MUL TISYNC MONITOR Compare the valuel Elsewhere you 'll pay $$$$ more.A complete AT computer on one PCB: simply add a case , power supply and drives! We 've see n th ese elsewh ere up to $1100! 14in Multisync VGA Monito r at a Board Solutions Bargain Basem ent price! Q: Do they replace faulty products? A: Or repair it. Make it look nearly new. Only a few scratches or marks. Maybe missing cables or manuals, though . .. Q: Do they continually visit overseas manufacturers for the latest products? ~ BABY TOWER CAS OUR PRICE Including power supply Perfect for our AT motherboard or baby AT motherboards. We include the power supply for what you 'd pay for the case elsewhere! $299 A: Yeh, sure: 24 hours after you ring for the third time! NOT JUST $545 S899 XT POWER SUPPLY Quality 150 Watt switch-mode power supply for XT or similar computers. $25 .00 OFF - Th is month only! WAS~ INC SUPPLY ! NOW ONLY All special prices apply until 30-1-90 sgg BOARD SOLUTIONS KIT COMPUTER BARGAINS: ASSEMBLE IT YOURSELF & $AVE! Model Speed Mem Floppy Hard Ports XT360 XTH32 ATH32 ATH42 640K 2x 360KBN/A 1xS,1x P $1495 640K 1x 1.2MB32MB 1xS ,1x P $1745 1MB 1x 1.2MB32MB 2xS,1xP,1xG$2395 1MB 1x 1.2MB42MB 2xS ,1xP,1 xG$2850 4.77110MHz 4.77110MHz 8112MHz 8112MHz Mono EGA VGA $2050 $2339 $2950 $3375 $2350 $2650 $3250 $3ij75 Please call for personalised configurations. A: Does travelling on the Manly Ferry count as overseas? BOARD SOLUTIONS IS YOUR ONE-STOP PC ENHANCEMENT COMPANY fl~S~'a BOARD SOLUTIONS Pty Ltd PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 5222 Assembled Systems $99 also available for only extra • Special prices available until 31 st January 1990 • 14 day money-back guarantee (except software) • 3 month warranty on all products • Mail orders our speciality • Freight on small items is $9.00 • Insurance $1 .00 per $100 of order value • All prices include sales tax • We accept Bankcard, Mastercard, Visa and Post Office COD • Call for our latest price list MS-DOS 4.01 & GW BASIC also available for on ly $155 extra MAJOR AUTHORISED STOCKISTS Adelaide Albany Broken Hill Charlestown Coffs Harbour Deniliquin Devonport Glen Innes lnverell Leeton Lightning Ridge Lismore Mackay Maryborough Morwell Mount Gambier Mt Isa Mudgee Nambour Narrabri Port Lincoln Taree Townsville Wagga Wagga Warnambool Windsor Microtroni cs Micro Electronics Hobbies And Electronics Newtronics Coifs Harbour Electronics Deni Electronics A1 Electronics John Summerlad Electronics Electronic Systems Leeton Audiotronics Cycle & Sound Decro Electronics Steven's Electronics Keller Electronics Morwell Electronics Hutchesson's Communications Outback Electronics Headware Nambour Electronics Namoi Computers Bassham's TV & Computer Brad's Electronics SuperSolex Phillip's Electronics Maartronics M&E Electronic Communication 2121799 412 077 884 908 439 600 525684 813 672 248 322 323 661 221 821 532 081 290 579 214137 511 723 214 559 346133 250 400 433 475 723 895 411 604 923 274 822 788 526 603 72 4466 216 558 629 870 775 935 DEALERS REQUIRED IN ALL AREAS.PLEASE CALL! JANUARY 1 990 FEATURES THIS ACTIVE ANTENNA can really help pull in those overseas stations. It comes as a kit and can be put together in a few hours. Details page 18. 4 Checking VCR Tape-Loading Problems by P. Hansen 10 82 86 100 Simple checks that you can make yourself Update On High Definition TV by Leo Simpson Impressive but not yet perfect The Technology Letters by Richard Kopf Adventures in the security industry The Evolution of Electric Railways by Bryan Maher Pt.27: a look at very fast trains Modifying The Studio 200 Amplifier by Leo Simpson One reader's suggestions PROJECTS TO BUILD 18 Active Antenna For Shortwave Listening by G. Swain ELIMINATE YOUR PHONE patch hassles with this easy-tobuild project. It's based on the MC34018 speakerphone IC and features a VOX circuit for automatic transmit/receive switching. See page 26. Helps pull in those overseas stations 26 Phone Patch For Radio Amateurs, Pt.1 by John Clarke Uses a VOX circuit for automatic switching 42 A High Quality Audio Oscillator by Leo Simpson Covers the frequency range from 10Hz to 109.9kHz 63 Speed Controller For Ceiling Fans by John Clarke Uses a light dimmer module SPECIAL COLUMNS 14 Vintage Radio by John Hill Obtaining the right spare parts 58 Serviceman's Log by the TV serviceman Sing it again Sam(sung) 66 Amateur Radio by Garry Cratt Yaesu's new FRG-8800 shortwave receiver 70 Computer Bits by Jennifer Bonnitcha Speeding up your PC - the options 73 Remote Control by Bob Young Designing UHF transmitter stages THE SERVICEMAN has a new vacuum desoldering station for those pesky ICs but the fault sure sucked him in. His problems start on page 58. DEPARTMENTS 2 Publisher's Letter 3 Mailbag 22 Back Issues 34 Circuit Notebook 57 Bookshelf 94 Product Showcase 98 Ask Silicon Chip 102 Market Centre IBC Subscription Page OBC Silicon Chip Binders THIS NEW AUDIO oscillator will put out high quality sine and square waves at up to 10 volts HMS and with 3-digit frequency resolution. Pt.1 starts on page 42. JANUARY 1990 1 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson , B.Bus. Editor Greg Swain , B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann (02) 982 9553 Regular Contributors Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler , MTETIA John Hill Jennifer Bonnitcha, B.A. Bob Young Photography Bob Donaldson Edltorlal Advisory Panel Philip Watson, MIAEE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Ply Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd , Rozelle , NSW 2039. Printing: Macquarie Publications Pty Ltd, Dubbo , NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year ( 1 2 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Ply Ltd , PO Box 139 , Collaroy Beach, NSW 2097 . Phone (02) 982 3935. Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBLISHER'S LE R Putting speed into perspective Did you ever stop to think how blase we have all become when thinking about electronics and technology? Try as we might, the march of technology is so remorseless that even quite dramatic developments tend to pass unnoticed. This thought came to mind this month when we were processing the first article on our new audio oscillator. At first sight, the specs of this unit appear to be fairly routine; pretty good but not spectacular. But in amongst those specs are the figures for rise and fall times of the square wave output which are quoted at less than 30 nanoseconds for the rise time and less than 20 nanoseconds for the fall time. These are pretty respectable figures and ones we are quite pleased with but that is not the real issue. The point is that these figures are really incomprehensible. When you start thinking in terms of nanoseconds you can have no real concept of what it means. None of us can. One nanosecond is one thousand millionth of a second! Trying to divide one second into such small intervals is pretty much on a par with thinking about the number of seconds in 32 years. If you don't believe me, work it out on your calculator. The truth is, of course, that when we talk and think about time intervals in terms of nanoseconds, we are not really thinking about normal time at all. In effect, we are thinking in terms of time standing still. And we use instruments such as high speed oscilloscopes to show us extremely high speed pictures of intervals "frozen in time". How else can we comprehend what is happening? Twenty years ago, it was most unusual to talk in terms of nanosecond time intervals as far as commonplace electronic equipment was concerned. Now such intervals are taken for granted, in computers and in all manner of consumer electronic equipment. Yet we are utterly blase about it all. One more point to consider: the devices which produce these very fast waveform transitions are very cheap. They include the 74C14 CMOS Schmitt trigger device which can be obtained for less than two dollars. Had we used a high speed CMOS version, the 74HC14, we possibly could have halved those rise and fall times. But that would be virtually meaningless, wouldn't it? Leo Simpson WOULD YOU CLEAN YOUR TEETH WITH A DAMP RAG? Sydney amateur TV is alive and well Following your presentation of the article on the "Gladesville GaAsFet Preamplifier" in the October 1989 issue of SILICON CHIP, I felt I should provide some background information on amateur TV in Sydney. The Sydney ATV Group has close ties with the Gladesville ATV Group which transmits live programs as well as WIA news, excellent AOCP training videos and other programs of technical interest. Gladesville transmits on Wednesdays from 1900 local. This program is re-transmitted on Friday evenings from 1900 local and there are transmissions on Saturday and Sunday from 1700 local. The SATVG has a gasbag net every Monday night at 1930 local with net control being viewed on UHF TV channel 35. The ATV repeater is crosslinked to a repeater on 147.300 MHz for those stations without access to channel 35 or for mobile or portable stations. ATV sound comes out on the repeater's output, while stations calling in on the repeater have their sound re-transmitted on channel 25. Access to our repeater is via 426.25MHz, horizontally polarised. If you do not have TV sound then 2-metre sound via 147.400MHz is retransmitted on channel 35. Our ATV simplex liaison frequency is 147.425 MHz and the repeaters are- Spr: ingwood in the Blue Mountains west of Sydney. A running test card and information pages are transmitted while the repeater is not in use. The SATVG also transmits the WIA morning broadcast every Sunday morning on channel 35 ATV sound. B. McNeil Winmallee, NSW af New service association In July 1989 there were moves to start a new organisation for people involved in electronic services across Australia. The new organisation, called EISA, standing for Electronic Services Industry Association, will be of particular benefit to a large cross section of technical people, whether they are in business for themselves or employed in service organisations. EISA is now incorporated in NSW and has a management committee drawn from business people involved in electronic services. The organisation is intended to be a professional organisation which will represent its members at all levels, from government to consumers. It will set and maintain standards and will have a code of ethics. Some of the electronic service areas which EISA will cater to include TV and VCR servicing, TV antenna installations, electronic parts/products sales, hifi sales and service, computer hardware, computer services, computer consultants and, in fact, any business that is related to the electrical/electronic industry. Some of the services that EISA will offer include a regular informative newsletter, member charge surveys, seminars on business and technical developments, Yellow Pages group advertising, liason with government instrumentalities with respect to self regulation, legal and accountancy services, dispute settlement assistance, consumer liason and custom stationery. For further information about the aims and services of the association, contact EISA, PO Box 154, Carlingford, 2116. Phone (02) 564 1991. Ray White Carlingford, NSW Omissions from articles on electric railways I wish to bring to your attention that acknowledgements to TNT Shipping and Development Ltd were inadvertently omitted from the October story on Australian Monorails. And in Part 21, the July 1989 episode on the NSW 86 Class Electrics, acknowledgements to the SRA and Comeng of Granville, NSW were also omitted. I thank the companies and departments concerned for their photos and the data supplied and apologise for these unfortunate oversights. Bryan Maher Alexandra Hills, Qld The Trackmate solution to dirty heads is the same as the dentist's solution for dirty teeth. Regular brushing, both up, down and from side to side, getting into all the places where dirt lingers. Trackmate's cleaning system consists of 2 purpose engineered brushes and 39,000 flexible absorbent filaments, 175% wider than a video tape. The unique marker pen applies pure isopropyl alcohol without mess or risk of overdosing. A good brush and wash every 100 hours will ensure the highest sound and picture quality. OTHER TRACKMATE CLEANER PRODUCTS ALSO 3.5" & MACINTOSH For your nearest retailer or distributor contact: ?l[l<at><at>!JJtnata·· AUSTRALIA PTY LTD (02) 428 4665 JANUARY 1990 3 Troubleshooting VCR tape-loading problems ,' By PETER M. HANSEN One of the most common VCR problems is the inability to properly load a tape. Here's /how to troubleshoot ·VCR tape loading problems. Servicing a VCR that won't correctly load a tape is usually a simple exercise, provided you know what to look for. However, it is important that you clearly understand the difference between cassette loading problems and tape loading problems. Reprinted with perm1ss1on from Radio-Electronics magazine, September 1989 issue. (C) Copyright Gernsback Publications, Inc., 1989. 4 SILICON CHIP A cassette loading problem is where the cassette carriage assembly dcies not properly accept the cassette (the shell) into the VCR. A tape loading problem is when the tape is not properly extracted from the cassette once the cassette is fully seated inside the VCR. Fig.l shows the basic VCR components. You should become familiar with them before attempting any servicing but right now our main concern is the tape loading process. To be able to see the inter- nal components, you first have to remove the VCR's top cover and head shield. You may also have to remove the cassette carriage in order to fully access the components involved in the tape-loading process. Fig.2 shows the cassette carriage being removed from a VCR - there are usually four Phillips-head screws on the top of the assembly that secure it to the VCR chassis. Fig.3 shows the cassette carriage assembly by itself. The gear block and motor assembly on the right side of the carriage is the drive system. This is used in front-loading VCRs to load the cassette into the VCR when it is first inserted. The VCR's guide rollers and slant poles are what actually extract the tape from the cassette and guide it IMPEDANCE ROLLER VIDEO HEAD DRUM ASSEMBLY A.C.E. HEAD CAPSTAN SHAFT PINCH ROLLER of the mechanism, with the video drum behind it. Tape-loading components GUIDE ROLLERS/ SLANT POLES IDLER SUPPLY REELS BRAKES BELT FIG.1: THIS PICTURE SHOWS the major components on a VCR chassis. These basic mechanisms will be found in all VCRs. across the video-drum assembly. The motor is located either above or below the mechanism and is usually driven by an integrated circuit that receives the motor load and unload signals from the VCR's main microprocessor. Fig.4 shows a typical tape-load motor located on the bottom of the VCR's chassis. In Fig.5, we see a load motor that is located on the top The load gear train is almost invariably located on the bottom side of the VCR chassis. The load gear train is connected to the load motor via a belt (or worm gear) and associated linkage rods and connectors. The load-gear assemblies are made out of hard plastic and have one and sometimes two cam gears with grooves that contain a lubricant. Fig.6 shows a typical loading gear train on the bottom side of the chassis. To get at components on the underside of the chassis, first make sure that the power is off and the unit unplugged, then remove the VCR's bottom cover. There are usually several Phillips screws securing the bottom cover to the chassis. Next, you have to identify the screws that secure the PC board to the chassis. Often, there will be identifying arrows printed on the PC board to indicate which screws must be removed. If you remove the wrong ones you may be dismantling the wrong thing. In some VCRs you must remove the front panel in order to release the PC board. Usually, the frontpanel assembly (which contains the switches, display etc.) is secured to the chassis by small (fragile) plastic retaining tabs. Give the unit a close visual inspection before attempting to remove the board so that you FIG.2: THE CASSETTE CARRIAGE assembly is usually secured to the VCR chassis by four Phillips-head screws. across the video head/drum assembly. After you select play or record you will see the two guide posts start the tape-extraction process; the video drum starts to spin anticlockwise (it reaches 30 RPM in about 3 seconds) and the pinch roller starts its short movement towards the capstan shaft. It is the action of the pinch roller "pinching" the rotating capstan shaft that actually pulls the tape through the machine during play or record. Most recent VHS VCR's use a dedicated DC motor to load the tape FIG.3: THE GEAR BLOCK AND MOTOR ASSEMBLY on the righthand side of the carriage is the drive system that loads the cassette into the VCR. JANUARY 1990 . 5 FIG.4: THE LOAD MOTOR is typically located on the bottom side of the VCR's chassis. FIG.5: THIS LOAD MOTOR is located on top of the mechanism, near the video drum assembly. Worn rubber belts are a common cause of VCR problems . don't crack anything. Remember that any mistake can lead to a gr eat deal of added expense. With the VCR placed in its service position [see Fig. 7) you can closely observe the loading components during a tape load. To do that, plug in the unit, insert an inexpensive test tape and hit the play button. As soon a s you hit play, you should see movement of the loading gear train as well a s the guide posts. 6 SILICON CHIP On many units you'll also see the cam gear as it shifts position from "stop" to "fully loaded" . Sometimes a mirror placed on your workbench sur fa ce can help you see both sides of the VCR's loading mechanism simultaneously. Diagnosing malfunctions A very common malfunction in VCRs is cracked, dirty or worn [slippery) loading belts. A ma jor symptom of this problem is that when the operator selects play or record, the guide posts will start their path toward the "V" stoppers (the metal brackets situated at the end of the loading grooves) but they will not reach the end of their path. Often, they will appear to have completed the loading process but closer inspection reveals that they only complete about 90% or 95% of their travel. The loading posts will then start retracting back toward the stop position and the video drum will stop spinning. This type of fault is usually due to a bad loading belt. Because the slipping belt prevented the guide posts from travelling their full distance, the microprocessor did not receive what's called the "load complete", the "after load" or, more simply, the " AL" signal. Some of the older units have a small microswitch embedded in the load gear train that is activated when the load posts are fully extended. However, most newer VCRs have infrared sensors built into the cam-gear assembly that transmit the various mechanical load stages during the tape-load mode to the microprocessor. In an aborted tape-load attempt, you will also be able to see that the pinch roller does not come in contact with the capstan shaft. The pinch roller will come in contact with the capstan shaft only when the system microprocessor receives a load-complete signal. A simple test for a malfunctioning load belt is to "assist" the load process with your finger [see Fig.8). With the VCR in its service position and a tape inside the machine, select the play mode; you should have your index finger or thumb placed gently on the load-motor shaft. You will feel the rotation of the load motor shaft against your finger . Wait for the load process to be completed (when the load posts appear to have reached the end of their travel) and then "assist" the load process by manually turning the load motor shaft in the same direction as it was turning by itself. If the belt is bad, the action of your finger will most likely complete the load. The load-complete signal will now be received by the microprocessor which will issue the signal to FIG.6: THE LOADING GEAR train is often covered by a protective plastic guard that must be removed to give access for servicing. This gear train is on the bottom of the VCR's chassis. FIG.8: A MALFUNCTIONING LOAD BELT can be checked out by "assisting" the loading process with your finger. FIG.7: A VCR IN ITS SERVICE position. A mirror on your workbench surface will allow you to see both sides of the VCR simultaneously. activate the pinch roller. A bad belt should be replaced but sometimes you can extend its life a bit by cleaning the belt and applying some rubber revitaliser. Sometimes the lubricant that is applied to sliding tracks and to various components dries up and hardens. This can cause much added friction for the load components and may cause the load to be aborted. If that's the case, you have to dismantle the assembly, clean off the dried-up lubricant, and apply a fresh coat. It's best to use a solvent like acetone for removing the old lubricant. It is also a good idea to first take a photo or make a quick sketch of an assembly before dismantling it for cleaning, so that everything goes back correctly. Often, there will be small alignment arrows imprinted on the gears - pay careful attention to any arrows, as they must be exactly aligned during assembly. If the load belt appears to be good and there is no dried-up lubri- cant, then you have to inspect the load gears for any signs of cracking - especially hairline cracks. Any gears that show signs of cracking must be replaced. Note that load motors do not usually go bad but if there is excess freedom of shaft movement, or any signs of excessive friction in the motor, it may have to be replaced. Another quick test of the loading system is to perform a tape load by hand, with the unit unplugged and no tape inserted. That will provide an unobstructed view of the loading mechanisms as they operate. Also, the loading process will be greatly slowed down, so you'll be able to see - and perhaps even feel- exactly when a problem occurs. You can then determine which part might be causing it to happen. To perform the test, turn the load-motor shaft by hand and observe the unit's operation. Watch for freedom of movement of all of the mechanical components involved in the loading process, and check for any obstructions that may impede proper loading. ~ VHS Cleaning Kit Tape heads and guides should be kept clean and the best way to do that is to use a tape cleaner on a regular basis. This VHS tape cleaner from Trackmate is different from most in that, as well as the fabric cleaning tape, it has auxiliary brushes to clean the pinch roller and the grooves in the tape head drum . The latter are liable to clog up and thereby prevent proper tape contact with the drum and heads. A convenient marker pen applies the cleaning solution, to eliminate any spills. The Trackmate VHS cleaner is available from most department stores at $39.95 . JANUARY 1990 7 David Reid Ele,troni,s NEWYEAR LABTECH 20MHz 2ch CRO with COMPONENT TESTER LASER "102" KEY KEYBOARD TO SUIT IBM "XT" • • • • • • $7 75.00 INCL TAX Deflection Factor: 5mV to 20V/0IV on 12 Ranges. Operating Modes: CH-A, CH-8, DU AL and ADO. Sweep Time: 0.2us to D.5s/OIV on 20 Ranges. Source: INT CH-8, LINE, or EXT. Includes 2 x 1:1 & 10: 1 probes 12 months Warranty. FOR DELICATE DUSTING NOW Standard 5 pin din connector EXCELLENT VALUE FOR ONLY $69.95 HURRY!!! DON'T MISS OUT ON THIS ONE 240V 120mm FAN • $16.95 $59.95 • • • IBM XT/AT compatible. Tracing Speed: 200mm/sec. Resolution: 195 dots/inch. 5.25" D.S.D.D. DISKS DB SERIES COMPUTE~R . _.,,,.. CONNECTORS .,,,,,.· • (SOLDER TYPE) NO NAME BRAND PKT-10 - "\ NOW ALL ONE PRICE $1.00 each • $6.45 SAVE!!! $14.95 ,, 3.5" D.S.D.D. DISKS NOW QUICK MOUSE • • • • • • • $26 .50 Fully Micros oft Compatible 6 0mm/sec tracking speed • 200dpi resolution Driver Test Prog ram and Pop-Up Menu Generator software supplied Includes Mouse/Pen holder and mousemat Ball in the centre design gives excelle nt control over movemen t Comfortable and natural hand grip 25 pin D Connector ONLY $89.00 IEC LINE UB-3 JIFFY BOX with METAL LID RG-62 COAXIAL CABLE • Multitap: 12V <at> 5 A 15V <at> 4A 24V <at> 2.5A Current drain 0 .25 amp AT THIS PRICE IT WILL BLOW YOU AWAY NO NAME BRAND PKT -10 M2175A TRANSFORMER 92 ohm MALE PLUG As used on PCs e 13 0 HURRY !! ! LIMITED STOCKS 41256 256K x 1 RAM CHIP INNER-EAR MINI STEREO HEADPHONES •12ons ~ i 1~Yn [ 1-9 $7.00 ea 10+ $6.30 ea IEC LINE FEMALE ~ SOCKET ~ $4.50 ea 68 x 4 1mm $1,.50/mtr $240.00/200 mtr roll I X $1.95 WAS $2.9 5 LOW VOLTAGE SPEAKER CABLE SP4 4" WOOFER $2.95 Great fo r speaker connection, alarm hookups and general voltage use. • Freq response: 62Hz-8kHz. • Sensitivity:8 0d8. • 8 watts RMS. • 8 ohms. WAS $11 .95 TOP VALUE!!! $15.00/1 oom roll NOW $10.00 • • As used on walkrnans etc . Complete with 6 . 5mm adapter an d spare pads <at>J _- $6.35 ea 27 V <at> 2 .2A 30V <at> 2 A • 240 volt PRI MARY $16.00 ea WAS $29.95 BE QUICK FOR THIS ONE11! PLUS RECEIVE A FREE MOUSE PAD DB-9 PLU G DB-9 SOCKET DB-9 BACKSHELL DB- 15 PLU G DB -1 5 SOCKET DB-15 BACKSHELL DB-25 PLU G DB-25 SOCKET DB-25 BAC KSH ELL Ideal for computers , amplifiers, etc. WAS $75.00 $ 14.95 ** * • WHITTY M0USE-C400 Ideal for cleaning model train layo uts, tiny PC boards, or hard to ~ get at electronic equ ipment. Also good for camera or computer eq uip. * * * * IBM " XT" compatible PLUS RECEIVE FREE: A 3.5 DIGIT MULTIMETER WORTH $57.00 (JANUARY ONLY) MINI VAC CLEANER ** • • iii Conductors: 2 x 1410.14mm 22 Z = IBM COMPUTER LEADS MEGGER METER KIT Insu lation breakdown can be determin ed by the use of this dual range megohm meter. Breakdown can be meaaured at either 500V or 1 000V depending on the required situation. Would suit electric ians or technicians work van, tool box or work bench . $ 79.00 • 08-25 MALEto CENTRONICS MALE 1.8 mtr • 08-25 MALE to CENTRONICS MALE 3 mtr • 08-25 MALEto CENTRONICS MALE 5 mtr $9.90 $27 ,95 $36.95 RS-232 SERIAL LEADS • 08-2 5 MALE to 08-25 MALE 1.8 mtr • 08-25 MALE to 08-25 FEMALE 1.8 mtr • 08-25 FEMALE to 08 -25 FEMALE 1.8 mtr CENTRONICS LEAD $19.95 $19.95 $19.95 • 36 PIN CENTRONICS MALE to MALE 1.8 mtr $24.95 SPECIALS ''Putting you into the 90s 11 PORTASOL ''PRO'' SOLDERING IRON KIT • • • Fully portable ! Gas Solderin g Iron, Blow Torch , Hot Blow, Hot Knife. Tip te mperature adjustable up to 400 deg C . Average continuous use : 90 minutes REPLACEMENT TIPS ULTRA-SONIC CLEANER • Ideal for cleaning drafting pens, watches , photographic filters, or even dentures . 2 4 0 volt operation. • NOW ONLY $75.00 SPARE TIPS AVAILABLE ONLY $1 50.00 EDM-1133 MULTIMETER EDM-1155 MULTIMETER • • • • • • • Autoranging and analog bar graph 3¾ digit, 0.6" large LCD 0.5% DC accuracy 8 functions EX TAX $175.10 "'~ ~~~~i:: • • $214.49 EX TAX 6 volt <at> 5000mAH Safety cut-out for short circuit protection. $29.95 ea $21.95 LITHIUM BATTERIES CR201 6 CR2025 CR2032 CR1 220 CR 1616 5 PIN DIN RIGHT ANGLE PLUG FUJI "AA" SIZE NICAD BATTERY $2.80 ea • 5 PIN DIN ALL ONE PRICE $4.50 ea ~~~t: COMPUTER DAT A SWITCH BOXES VALVES ARLEC DIGI-SCALE $59.95 f.~ ~ 1.2 volt <at> 500m AH 8 PIN MINI DIN JOINER Handy for cable extensions $2.95 ea ll EX TAX • DI GI -SCALE will measure from 1 gram or 0 . 1 ounce up to 2kg or 41b 4oz . • Convert from grams to ounces or ounces to grams usi ng a selec ted key. • Vario us items can be individually we ighed in the same container using the reset key. • 240 volt (plugpack not suppl ied) or battery operated . • 1 2 months warranty. ONLY CHARGER $27 .95 Bonus 2 Nicads FREE FROM $8.45 $248.00 INCL TAX 6 VOLT LANTERN RECHARGABLE BATTERY BY ARLEC TTERY • Compact size • Recharges 2 or 4 AA Nicad Batteries • Two (2) charging rates - 4 hours, 15 hours • 2 year guarantee 6AQ5 . 6AU4 6V6 . 6B05 12AX7 . .... 12AT7 PY500 . . . . RL519 6D06 . . ... 6L6 6GW8. 6CA7 14 functions including Frequency and Capacitance Measurement , Peak and Data Hold, Max and Min Memory t Standard accessories: ,/ . . Test lead , manual , spare fuse Dimensions: / 17 4mm(L)x82mm(W)x38mm(H ) / $203.00 INCL TAX Autoranging and analog bar graph e 3¾ digit, 0 .6" large LCD Dimensio ns: 17 4mm(L)x82m m(W)x38mm(H) INCL TAX • • Standard accessories: Test lead , manual, spare fuse Standard accessories: Test lead, manual Dimensions: 17 4 mm(L)x82 mm(W)x38 mm(H) $172.00 $148.82 Autoranging and analog bar graph 3¾ digit, 0 .6" large LCD 0.5% DC acc uracy • 12 functions You can't pass these up at this price. $9.95 ea SOLDER SUCKER TOOL DB-25 TYPE and CENTRONICS TYPE • • 2-WAY was $59.00 NOW $49.00 4-WAY was $89.00 NOW $79.00 Replacement tips $2.35 ea Long life teflon tip Self cleaning plunger $10.00 ea PLUG-PACK POWER SUPPLY • Multi-voltage 3, 4 .5, 6, 7.5, 9, 12 volt 500mA $15 .00 Many uses around the home or workshop. W PHONE NOW!!! (02) 2671385 TO PLACE YOUR ORDER David Reid Electronics 127 York Street SYDNEY 2000 Ph: (02) 267 1385 MAIL ORDERS P.O. BOX 0103 SYDNEY 2000 FAX: (02) 261 8905 POST & PACK $5-$25 .... $4 $26-$50 ... $5 $51+ .... . $8 BUSINESS HOURS Mon-Fri 8.30-5.30 Thur 8.30-7 .00 Sat 9.00-1.00 •---• VIS4 mpressive but not yet perfect During November 1989, both the Japanese and European systems of high definition television (HDTV) were displayed in Sydney, coinciding with a conference hosted by the Australian Broadcasting Tribunal entitled "Television 2000: Choices & Challenges". By LEO SIMPSON The Japanese were first into the HDTV arena and had prototype systems on display as long as 10 years ago. Their system is 1125 lines at a field rate of 60Hz - many people would have seen it at Brisbane during Expo 88. But in the last three years or so, the Europeans have put in an enormous effort and have now produced a full line of HDTV equipment from cameras and recorders to large screen CRT and rear projection TV sets, all in the new wide format. The European HDTV standard is 1250 lines and 50Hz - much closer in compatibility to our present PAL system of 625 lines and 50Hz. Considering that the Europeans have had to go from a standing start, they have made a prodigious effort. Unfortunately, it was not possible to make side-by-side comparisons between the Japanese and European systems since they were on display at different venues - the Japanese at the Hilton International Hotel and the European system at the Sydney Opera House. And as it happened, we saw the two systems on different days in the same week. 10 SILICON CHIP In spite of this, we can report on the similarities and differences between the systems and though you might not expect it, they are considerable. In fact, when you come right down to it, the two HDTV systems are exactly the same in only one respect - the new wide aspect ratio screens. These wide screens used to be referred to as having an aspect ratio of 5:3.33 (as opposed to the 4:3 aspect of conventional TV screens). HDTV wide scr.e en format is now referred to as 16:9 which is somewhat easier to say and think about. Either way, the wide screen format is the same as used in cinema theatres. Fine line structure When you look at a large conventional TV screen from a distance of one metre or so, you are conscious of the horizontal scanning lines and of the vertical dot structure. In HDTV screens of much the same size and at the same viewing distance, the line structure is no longer apparent - you have to look closely to see it. The picture tubes also have a much finer pitch. So these two factors are the main differences between HDTV and current PAL TV as we know it. The wide format screen is more attractive than the current format but this in itself is not enough to make you long to see HDTV introduced. TV sets using the wide screens are extremely bulky by the standards we have become used to. For example, a 16:9 aspect TV with a screen 60cm wide will have a cabinet which is very deep at around 60cm or so. Some of the current widescreen sets using picture tubes would be difficult to get through the doors in many homes. This is because the widescreen HDTV tubes are using 90° deflection yokes rather than the 117 ° of current TV picture tubes. At least, we assume that the tubes are 90° deflection, to obtain better convergence. There is no other reason to explain the great depth of the sets. This is a factor which would probably make most people decide against a HDTV set in their home. They are far too bulky. Wide projection screens Ah, but what about HDTV rear projection sets? The Japanese and Europeans had 50-inch (127cm) rear projection HDTV sets on display and these are truly impressive. It is these sets that most people were drawn to. While not quite as bright or as sharp as the picture tube sets, their very size is the attraction. And they are nowhere near as deep as the sets with picture tubes. •◄ ,, "..- . h ,:: . , -: , In Europe, they are getting ready for D2-MAC broadcasts via satellite . The Europeans see D2-MAC as the first step along the road to high definition TV. Our reaction was that when HDTV is introduced into Australia (and we have no doubt that it ultimately will be), most sales will be of the really large rear projection sets. As far as we are concerned, if you are going to go for HDTV, you may as well go the whole hog. The day of the "theatre in your home" will be at hand. However, it was the large screens which brought to light a disadvantage of the European HDTV system - flicker. Because their screens are so much wider you have a much wider field of view and therefore more visual information coming into the corners of your eyes. And so you are more sensitive to flicker. By contrast, the Japanese system, operating at 60Hz, has no flicker at all. If the European system is to succeed, it will have to increase the field rate, by means of a field store in the receiver, to 100Hz. 100Hz sets based on the DZ-MAC system were also on display during November, 1989. Paradoxically, the HDTV system displayed by the Japanese did not appear to have enough "high definition". Actually, the Japanese had two HDTV exhibits. One, using a 120-inch screen, was using the full 30MHz bandwidth video and was truly spectacular - as good as, if Philips showed this impressive 50-inch rear projection HDTV set during the Eureka demonstrations in Sydney. HDTV sets use screens with a 16:9 aspect ratio as opposed to the 4:3 aspect ratio of conventional sets. not better, than 35mm film. The second HDTV display, which had one 50-inch rear projection screen and a variety of wide format picture tube sets, was using video signals processed by MUSE (MUltiple Sub-nyquist Sampling Encoding). This is a complex video encoding bandwidth compression system which gets the necessary signal bandwidth down to 8.1MHz to make it suitable for satellite transmission. Bandwidth reduction One of the tricks used by the MUSE system is to reduce the video bandwidth more for moving picture information than for stationary pictures. Maximum reproducible luminance bandwith for stationary pictures is 22MHz while chrominance bandwidth is 14MHz. By contrast, effective luminance bandwidth for moving picture information is 14MHz and the chrominance bandwidth is even less, at just 3.5MHz. The reduction in bandwidth for moving picture information is justified by the MUSE system inventors, NHK Science and Technical JANUARY 1990 11 The Japanese also showed a 50-inch.:rear projecti?n set at t_heir Sydney demonstration. Large screen size will be the mam attraction of HDTV. Research Laboratories, on the basis that the human eye is more tolerant of image blurring when objects are moving. Be that as it may, our impressions of the MUSE images, displayed on both rear projection sets and wide format picture tube sets, were that there was just not enough bandwidth. All the pictures were via tape and there was a general lack of really finely focussed, bright and sharp images. On the few closeups of faces that were seen there was none of the sharpness that can be seen from first class PAL TV images - individual hair strands, wrinkles, skin pores and so on. Why weren't these present? We have to assume lack of sufficient bandwidth. Europeans came from two sources. The first was direct video from a camera aimed at Sydney's Circular Quay. The images were bright and very sharp - no apparent lack of bandwidth here, even though a similar degree of bandwidth compression is employed. There was also a variety of taped video including scenes from the French Bicentennial. While the latter could only be summed up as tedious television, the images were bright and sharp, even on the rear projection sets. The footage from the French Bicentennial also included some night scenes which demonstrated that the new HDTV Plumbicon camera tubes have quite good lowlight sensitivity. The European experience Eureka is the name given to a cooperative venture backed by European governments and by ma- On the other hand, the HDTV picture information displayed by the Eureka and HDMAC Developed by Philips, this S-VHS video recorder features a built-in D2-MAC decoder and can also be linked to a Eurocrypt pay TV card reader. 12 SILICON CHIP jor companies such as ThomsonCSF (France), Bosch (Germany), Philips (Netherlands) and some 30 odd others. Over 600 engineers are working on every aspect of HDTV - from cameras to recorders and receivers. The system will embrace satellite and cable TV systems and has encryption for pay TV systems. It also has large data transmission capability and up to eight sound channels. The basis of the new European TV standard is DZ-MAC which is similar to but not compatible with the B-MAC system used by Aussat and the ABC for outback TV services via satellite. MAC stands for Multiplexed Analog Components and is a time division system which transmits the sound, luminance and chrominance information in a sequence for each line rather than frequency multiplexed together as in the PAL and NTSC systems. B-MAC and DZ-MAC are said to give 50% more picture bandwidth than PAL and indeed they give a brighter, sharper picture. HDMAC is the HDTV version of DZ-MAC and the Europeans are heavily plugging it since it is compatible with DZ-MAC which, in turn, is said to be more readily compatible with the existing PAL system (via decoders) than the Japanese HDTV system. HDMAC also involves substantial bandwidth compression to make it compatible with DZ-MAC but the ultimate picture quality appears to be better than Japanese HDTV pictures processed via MUSE. One point is clear. The Europeans have come far enough in three years to make sure that the Japanese will no longer have all the running in HDTV, at least not in countries which presently have thePAL system. In fact, it is clear that the Japanese are going to be shut right out of Europe with HDTV. As far as Australia is concerned, we will probably get HDTV via a cable pay-TV system and that will possibly be in the late 90s. What system will we use? Who knows but no decisions should be made by the government at this early stage. As far as we were concerned, after seeing both versions, HDTV is good but NYP - "not yet perfect". ~ • • • • • • • • • Disk Cases DD50L DD100L DD40L DDSOL DD10 50 x 5 1/4 100 x 5 1/4 40 x 3 1/2 80 x 3 1/2 10 x 5 1/4 Basic Ranges $25.80 Vdc $29.95 Vac $25.40 Ade $29.95 Aac $2.95 _Ohms Disk Cleaners FDCl FDC3 3 3/4 digit large LCD display 4000 count resolution 41 segment analog bar graph Data Hold Max/Min stores highest and lowest readings Relative display (Offset) Continuity beeper Diode check Freauency to 40kHz 51/4 3 1/2 $6.95 $6.95 400mV to 1000V (±0.3%) 400mV to 750V (±0.5%) 400mA (100µA) to 20A (±0.5%) 400mA (100µA) to 20A (±0.5%) 400n 100mn) to 40Mn (±0.5%) see Review in Silicon Chip November 89. Accommodates up to 24 14-pin ICs and has all the IBM signals brought out to pin sockets on the board. Includes DB25 female socket for e)(ternal connections. Suits AT/l(T or compatibles ..$87 .99 NiCad Chargers MALE IEC PLUGS Ideal for connecting monitors to IBM PC's so you switch both on and off together! $6.35 Check us for all your IEC Connector Requirements We Carry AWide Range in Stock $144 AT&M KITS Locally produced super quality kits for the professional user.See AT&M advertisments and E.A. Dec for full details . For example ATM20 Infra• Red Barrier has 15m range, 2 outputs. Uses no lenses and detects d down to 10mm diameter. Uses high frequency coding to increase range and reduce interference. Special GaAIAs transmitter with crystal control and Another of our special '"Strip·· low noise PIN diode detector. purchases and you can make Excellent value at $39 .60 savings on these capacitors which Kit Description Price are preformed for loading on to ATM01 3 digit Counter $33 .60 pcbs. 25 capacitors on each strip for ATM02 4 digit Counter 50.40 just $1 .50. Crazy that's just 6c ATM03 3 1/2 digit DVM 59.40 each!! ATM04 1Hz Timebase 22 .40 1µF, sov ATMOS Fibre Optic Modem 75 .00 22µF, 10V ATM06 Reciprocal Calculator29.40 33µF, 25V ATM0710MHz Timebase 45.60 47µF,50V ATMOS V/F Converter 42.60 220µF, 10V ATM09 FN converter 42 .60 Also we have the 1N4007 still at ATM10 Quad Power Supply 60 .60 $1.50 per strip of 25 (see December ATM1110 Minute Controller 46.20 advertisements) ATM126 dig Batch Counter 75.00 ATM13 3 Digit Counter 65 .40 ATM14 3 1/2 digit LCD DVM 42.60 ATM1610kV Isolator 70.80 Two models to choose from: ATM17Storage Adaptor 193.00 NBC·3 charges AA, C, D and 9V ATM188 bit UART 66 .00 cells Handles up to 10 equal sized ATM196 dig Up/On Counter 69.60 cells' or 3x9V at same time. Will also ATM20 IR Transceiver 39.60 handle mixed sizes. LED indicators ATM21 Multi-Timebase 42.60 $54.95 ATM2216Ch Tranmitter 77.40 NBC-2 is designed for AA and AAA ATM2316Ch Receiver 77.40 cells and charges 2, 4 or 6 cells at a ATM24 22/3 Comms PCB 34.80 time. LED indicators. $22.95 ATM25 22/3 Radio Modem 66.60 Electrolytic Caoacitor Special UP604 IBM Breadboard Card GrBIII V11lue 11I ONLY NEW CATALOGUE Did you get your copy of our new catalogue in December's Electronics Australia? If you didn't then ask for a copy with your next order. This issue has a list of all the most wanted semiconductors Emtek ELogic Probe • Level Detector • Pulse Detector • Pulse Memory • Hi/Low/Pulse Leds • Two Tone Beeper • Suits TTUCMOS/HTL etc • Operates from 4.5 to 20Vdc Specifications Max Input Frequency 17MHz Min Pulse Width 30nS Input Impedance 1Mn Over-Voltage Protection 220Vac Pulse LED flash time 500ms $31.50 ®- 4-· Save $12 this month only on the WTCPS Soldering Station . Transformer powered low voltage features Weller closed-loop method of controlling maximum tip temperature to protect temperature sensitive components. • 48W stainless steel heater • Non-burning silicon rubber cord e 15 tip sizes• 0.8mm to 6.00mm • 11secs to recover for 37°C drop • Choice of tip temperatures 315°C/ 600°F 370°C/70°F 430°C/800°F Save $12 Now $125.00 GEOFF WOOD ELECTRONICS PTY LTD All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED ::0 ~ a CJ ci ::o ~f-~ /f:I, Weller Soldering\r~ \, Iron Special t(c3 . 229 Burns Bay Road, (Corner Beatrice St.) INC IN Nsw Lane Cove West, N.S.W. P.O. Box 671, Lane Cove N.S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $5.00 to cover postal charges. Next day delivery°in Sydney add $5.00. .,, a 2 "t, g ~ ri ::: ~ : .,, a J:l ri ::i: ~ VINTAGE RADIO By JOHN HILL Obtaining the right spare parts Collecting usable valve radio spares is an essential aspect of vintage radio restoration. For this reason, you should make every attempt to obtain old receivers in any condition. Now I'm fairly reluctant to admit this but I have just paid $30 for a totally derelict 54-year old console model Radiola. To make matters worse, it is a near useless battery set, thus making my purchase even less of a bargain. This wreck of a radio has been neglected for so long that its rightful place is at the rubbish tip and it is truly remarkable that it has survived for so long. I found this treasure in an antique shop and the dealer had the gall to have a $40 price tag on it. After a lengthy barter, the dealer simply told me that the set had cost him $25 and that he really couldn't afford to sell it for less than $30. While $30 was an outrageous price for such a pile of junk, I bought it because it contained a part for which I had been searching for nearly three years - the dial escutcheon. Now while $30 may seem a lot to pay for a small rectangular moulding of black Bakelite, the price is not as bad as it may appear to be. The set that required the escutcheon was purchased for only $5 so, all things considered, I still bought a reasonably cheap console radio. Incidentally, the above price differences are a good indication of the increasing value of old valve This is the $30 escutcheon from the old Radiola mentioned in the text. The lack of this particular part delayed restoration of an old receiver for three years. 14 SILICON CHIP radios. Even so, I am quite sure that this battery Radiola would have stayed in the corner of that antique shop for a long time if I had not bought it. It was not worth $30. Other parts Apart from supplying the much needed escutcheon, the old Radiola will also supply a number of other useful spare parts. Items such as the dial, dial drive mechanism, knobs, tuning capacitor, etc are all common with the mains-powered version and will be stored away for some day in the future when, once again, a mid-1930s Raidola will require some bits and pieces. The cabinet on this old battery receiver is also worth a mention for I have never seen one in such a poor state. It had been wet for so long it was starting to rot away. Someone had even nailed a tomato stake to it to prevent the base from separating from the rest of the cabinet. It was one of those repairs that can best be described as "untidy but strong". However, while such a cabinet may be totally unrestorable, the loose veneer was removed and put aside for cabinet repairs. Often a cabinet requires a small patch of veneer, particularly along edges where it sometimes chips away. I especially wanted to restore one of these old Radiolas for it was this model radio that lived in our lounge room at home when I was a lad. It was on one of these stylish consoles that I listened to "Superman", so you can imagine the nostalgic feelings I would have for this particular make and model. Finding a suitable escutcheon after looking for so long was indeed to be wrecked and which are to be put aside for possible future restoration. 5-valve Healing This 5-valve Healing is the product of three individual radios. Although all three were different models, the parts needed to complete the restoration (ie, the cabinet and speaker grille) were interchangeable. pleasing for the restoration can now be completed. Vintage radio collectors who are at all serious about restoring old radios must try to gather up as much radio "junk" as they can lay their hands on. Many a restoration is impossible without the correct replacement parts. Just one missing component (such as an escutcheon) will prevent the job from being completed. Of couse, after many years of scrounging an acute storage problem arises. But if you are going to collect old radios, then collecting usable bits and pieces is part of the fun. My opening story about the Radiola that waited three years for a suitable escutcheon is just one of many similar stories that can be told about some of the receivers in my collection. This lesson was learnt early on when several incomplete radios were wrecked only to find out later that they could have been restored when another radio of the same make and model was found. After this realisation, one becomes more careful in choosing which sets are A problem of this nature cannot be solved without the right spare part. The lack of such a spare can prevent the restoration of an otherwise complete and working receiver. One particular example that comes to mind is a Healing mantel model that was given to me. There were two problems regarding its restoration. First, someone had drilled three holes in the front of the cabinet so that extra volume controls could be added (these controls directed the audio output to a network of extension speakers). Second, the white plastic speaker grille had been badly damaged and several of the vertical bars were missing. While such a set sounds like a logical one to wreck, I was reluctant to do so because I could see distinct possibilities in it and I thought it would be a good one to restore. My reasons for liking the old Healing were: its excellent 5-valve performance, its Bakelite cabinet, and its unusually large 8-inch loudspeaker which gave the set a remarkably good tone. So the set was put aside in the hope that something would come along - and come along it did! Some time later I had the opportunity of buying up a whole heap of radios and amongst them were not just one of the previously mentioned Healings, but two of them. Although one had a smashed cabinet, I felt confident that my search was over. Once I got them all on the workbench, what originally ap- Although not quite the same as the original dial (left), this dial can be used as a replacement. An extensive range of radio spares is essential for the vintage radio enthusiast. JANUARY 1990 15 zone was complete and in restorable condition without scrounging parts from other sets. This particular receiver polished up quite well and while it took a considerable time to repair the dial mechanism, the finished result was very pleasing. It is shown in one of the accompanying photographs. No sooner had that old Airzone been placed on the shelf when two other similar sets arrived on my doorstep. Once again, these two are also restorable and should not be a problem to repair. The three Airzones are a complete contrast to the Healing in that the Healing was the product of three different receivers. It's feast or famine; one has either an abundance of one thing or a shortage of something else. In contrast to the Healing, these three Airzones can all be restored without having to scrounge parts from other sets. The one in front has already been restored. peared to be three identical receivers turned out to be three entirely different models. The original set was a broadcast band 240V mains operated set, while the other two sets were battery models. One was a straight battery set while the other had a vibrator unit. Both battery receivers were dual-wave types. Fortunately, the bits required to complete the restoration [a cabinet and a speaker grille) were inter-changeable on all three models and a nicely restored receiver eventual- ly emerged from a substantial pile of unrelated bits and pieces. A fourth set of this type came along some time later and although it was a 240V version in going order, it also had a smashed cabinet. It's strange that of four similar radios there was only one cabinet that could be used. The reason is probably purely coincidental because the cabinets were quite sturdy Bakelite types. Also among the aforementioned "heap of radios" was a 5-valve Airzone. Unlike the Healings, the Air- Missing knobs All too often a restoration cannot be completed because of a part that is either broken or missing. Perhaps the most common and the least troublesome missing component is a lost control knob. However, in some instances a missing knob is a major loss because there are odd sets that use special purpose knobs and only the correct replacement will solve the problem. One easy way out of a missing knob problem is to fit a complete set Special knobs, such as the dual control type shown here, can make restoration work difficult. The large knob is the on/off switch while the smaller one controls the tuning. ◄ •:..-&·. .j 16 SILICON CHIP Left: the somewhat derelict Radiola cabinet mentioned in the story. It had been badly water damaged and some of the timber was beginning to rot. No wonder the author was reluctant to admit paying $30 for it . VINTAGE RADIO REPAIRS LAWSON RADIO has been in the business of repairing radios for 40 years. If John Hill's column has rekindled the memories, but you are not confident enough to carry out your own repairs then call us now, for an obligation free quotation. A missing knob? If only that's all it was. The real problem with this Lekmek receiver is the cabinet. Someone has had a go at it before and has sanded through the veneer in at least half a dozen places. of a different type. A complete set of knobs of the same style always looks better than an odd assortment. However, to do this one needs to keep a comprehensive collection of control knobs. While there are many styles of knob that may suit a particular receiver, most collectors will immediately pick up the fact that the Wanted: a complete set of innards for this old cabinet. It will probably end up with a non-genuine mismatched receiver and hardly anyone will ever know the difference. receiver has the wrong knobs on it. Therefore, it is important that one has a good range of spare knobs so that the right part can be supplied to maintain the set's originality. Many of the old sets, especially those from the 1930-40 era, had rather appealing knobs that came in many fancy shapes and designs. It would not be difficult to make an interesting display for there are many varieties and a complete collection would have many hundreds of knobs in it. Unfortunately, when it comes to finding the right knob, Murphy's law prevails and the knob you want is always the one you haven't got no matter how many knobs you may have. Missing, broken or worn parts are always a problem for any vintage radio collector. Often a set can be missing quite major components such as loudspeakers, power transformers or a few hard to get valves. One of the "in waiting" sets in my garage is not really a set but an empty cabinet. Whether that cabinet ever becomes a working radio again depends on finding suitable innards. But as this particular cabinet is one of those elegant types with turned legs and ornate fret work around the speaker opening, I am keen to see it working again - even with a non-original chassis and speaker. lltl Should you want to sell or purchase a vintage radio contact Michael today. 298 GREAT WESTERN HWY LAWSON, NSW 2783 (047) 59 1254 D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS • for Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST Quartz in filter 10.9MHz 6kHz BW $12.50 US Filter capacitor 4µF 3kV .... _$15 .00 Electromagnetic Airpump for Aquarium .... $9.00 Timer Motor 240VAC 6RPH. . . $6.00 Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Callex Service Station In Blrdwood Road) Phone 724 6982 TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. JANUARY 1990 17 Interested in shortwave listening? This active antenna can really help pull in those overseas stations. It comes as a kit and can be put together in a few hours. By GREG SWAIN ACTIVE ANTENNA for the shortwave bands Shortwave listening is a popular pastime for many people and the new receivers now available make tuning into the world easier than ever before. Unfortunately, making the most of those weak signals from across the world generally requires a longwire antenna but that's not always convenient. There is another way and that is to use an active antenna. The "World Tuner AT4 SW" active antenna described here uses a 1-metre telescopic antenna, a tuned circuit, and two transistors to prevent loading of the antenna and to boost signal output. It covers the shortwave bands from 3-30MHz but by plugging in an external inductor, you can cover other bands as well. The unit is disarmingly simple in appearance. The circuitry is hous- ed in a small plastic case and this is fitted with a mounting base which accepts the telescopic antenna. When not in use, the antenna can be telescoped down and stored out of the way by fitting it to two plastic P-clips on the back of the case. The three user controls are arranged along one side of the unit. They include a 4-position band switch, a tuning control and a power switch with LED indicator. Also fitted to the unit are three 3.5mm jack sockets for external antenna (EXT ANT), signal output and external inductor (EXT L). To use the unit, you simply connect the output to the antenna input of the receiver, select the required band and adjust the tuning knob for best signal. What could be easier? Because it can tune out interfering signals and noise, the "World Tuner" can outperform many longwire antennas. Often, it can turn a station that is virtually unreadable into a clear signal. Alternatively, for even better performance, the unit can be used to boost the performance of an existing longwire antenna via the external antenna input. In short, the active antenna can really help lift those weak stations "up out of the mud". We tried it with a Sony ICF-2001 shortwave receiver with great success but the unit will work well with any receiver, particularly those that lack sensitivity. The circuit Fig.1 shows the circuit details of the active antenna. Normally, the telescopic antenna is in circuit but this is switched out if an external antenna is plugged into the EXT ANT 18 SILICON CHIP +3V ON S2b OFF~ 15pF LEO1 ON 01 2N5485 02 BC548 C L2 ---=B+--1 220k II 3V....?... + .,. 3.3uHII II 1k L3 1lffiS1a 6.8uHII II - 52 , C B -20d8 VClb A 1 1 .,. L4 60pF 11 louTPUT 15k 82!1 .,. .,. B II 15uHII 100pF -:.::o--.J .,. G<at>o ELJc VIEWED FROM BELOW WORLD TUNER AT4 SW Fig.1: signals from the antenna are fed to an input tuned circuit which is selected by S1a & Sib. Q1 and Q2 function as buffer stages to prevent loading of the antenna tuned circuit. jack socket. The signals picked up by the antenna are fed via a 15pF ceramic capacitor to a tuned circuit consisting of either VCla or VClb and either 11, 12, 13 or 14. Slider switch S1 selects the band to be tuned. There are four bands: 3-9MHz, 5-14MHz, 10-20MHz and 18-30MHz. When Sl is in position A, 11 and VCla are selected and the antenna can be tuned from 3-9MHz. Similarly, position B selects 12 and VCla, position C 13 and VClb and position D 14 and VCl b to tune the remaining bands. Alternatively, an external inductor can be plugged into the EXT L socket to extend the tuning beyond those ranges provided. For example, plugging in a 47 µH inductor (supplied with the kit) extends the tuning range down to about 1.83MHz. A 560µH inductor will be required if you want to cover the AM broadcast band. Note that when the external inductor is plugged in, it automatically disconnects the internal 15µH inductor. This means that Sl should be switched to position A when using an external inductor. FET Ql forms a high-impedance buffer stage for the antenna tuned_ circuit. It is wired as a source follower and so has a gain of a bout 0.75. Its output is fed to S2a, which selects between OdB and - 20dB attenuation levels, and thence to the base of Q2. Q2 functions as an emitter follower. DC bias for this stage is set by the 10k0, 15k0, 4700 and 820 resistors. The signal output is taken from across the 820 resistor and coupled to the output jack socket via a .OlµF capacitor. Power for the circuit is derived from two 1.5V batteries and is switched by S2b. LED 1 provides power on indication but can be deleted if you want to increase battery life. Building it This project is available as a kit of parts (see panel) and is supplied ready to assemble. The case even When the unit is not in use, the antenna can be telescoped down and stored by sliding it into two plastic P-clips on the back of the case. JANUARY 1990 19 The two bottom terminals of the jack socket are soldered directly to the board while the third terminal is connected using a wire link. Most of the parts are mounted on a small PC board. Push all the parts down onto the board as far as they will go before soldering their leads. The four inductors are all mounted end-on. ~-----==----~f----CASE WASHER/ ,._____NUT Fig.2: here's how to install the plastic P-clips on the back of the case. comes pre-drilled and silk-screened to make the job as easy as possible. The order of assembly is as follows: • Step 1: fit the P-clips to the back of the case [see Fig.2), then affix the base weight to the case lid using contact adhesive; OUTPUT • Step 2: screw the extension shaft onto the tuning gang shaft. Note: hold the flats on the tuning gang shaft with a pair of pliers when fitting the extension shaft, otherwise you'll damage the gang. • Step 3: assemble the PCB as shown in Fig.3. Note that the tuning gang and 3.5mm jack socket are mounted on the copper side of the PCB while the switches go on the component side. Before mounting the jack socket, bend one of the terminals at the rear of the jack socket through 90° and then cut off the eylets of the two terminals to be soldered to the board. A soldering iron with a very fine tip is required to solder the socket terminal near the edge of the board. The remaining terminal on the rear of the socket is connected to the PCB using a wire link. Push the switches down as far as they will go before soldering their terminals. Inductors 11-14 are all installed end on around Sl while Q2 is laid flat against the PCB (see photo). Install the LED so that its tip is about 23mm above the surface of the PCB [the longest lead is the anode). By the way, the four on-board inductors all look like resistors. They have colour bands , just like resistors, but are easily identified because the fourth band is always silver. The colour coding for each value is listed in the table adjacent to Fig.3. • Step 4: install the batt6ry clip EXTERNAL~ ANTENNA lG - 1 CERAMIC & MONOLITHIC CAPACITORS □ □ □ □ No 1 2 1 2 Value 0.1µF .01µF 100pF 15pF IEC 100n 10n 100p 15p EIA 104 103 101 15 INDUCTORS - + JV - EXTERNAL INOUCTOR BATTERY Fig.3: install the parts on the PCB as shown here. The capacitor and inductor codes are shown in the adjacent tables while the resistor values can be checked using a digital multimeter. 20 SILICON CHIP □ □ □ □ □ No 1 1 1 1 Value 47µH 15µH 6.BµH 3.3µH 1µH Colour Code yellow purple black silver brown green black silver blue grey gold silver orange orange gold silver brown black gold silver PARTS LIST The tuning capacitor is also installed on the copper side of the PCB and is secured using the screws provided. The leads to the output and external antenna sockets are run directly to the back of the board. 1 plastic case (pre-drilled & screen printed) 1 metal weight for lid 1 telescopic antenna (1-metre long) 1 antenna mount assembly 4 rubber feet 1 32mm-dia. knob 1 extension shaft 1 rubber cap (for external 4 7µ,H inductor jack) 2 P-clips 1 tuning capacitor 1 DPDT centre off toggle switch 1 4-position slide switch 1 PCB, code Technikit WT401 3 3.5mm chassis sockets 3 3.5mm jack plugs 1 output lead 1 double AA battery holder 1 battery snap connector 1 solder lug 1 carry case (optional) Semiconductors 1 2N5485 FET (01) 1 BC54 7 A transistor (02) 1 5mm red LED Capacitors 1 1 2 1 2 4. 7 µF tantalum 0. 1µ,F monolithic .01 µ,F monolithic 1 OOpF ceramic 1 5pF ceramic RF chokes 1 4 7 µ,H (in jack plug) 1 1 5µ,H 1 6.8µ,H 1 3.3µ,H 1 1µ,H The PCB is secured inside the case by installing the nuts on the toggle switch and on the EXT L socket. Be sure to tighten the antenna base securely to prevent it from turning when the antenna is installed. lead (red to positive) by looping the leads through from the copper side of the PCB. • Step 5: remove the washer from toggle switch and install it on the board mounted socket. Mount the other two sockets adjacent to the Pclips on the rear panel and install the antenna mount and solder lug as shown in Fig.3. Tighten the antenna mount screw firmly. If you don't do it up tight enough, the antenna mount will twist when you screw in the antenna. • Step 6: complete the wiring as shown in Fig.3, then mount the PCB in the case (the washer on the EXT L socket goes inside the case). Check that the LED protrudes correctly through the front panel and adjust if necessary. Complete construction by installing the nuts on the EXT L socket and on the toggle switch, and by screwing on the lid and rubber feet. Testing The test procedure simply involves hooking the active antenna Resistors 1 220k0 1 15k0 1 10k0 3 1k0 2 4700 2 820 Miscellaneous Screws, nuts, washers, insulation for battery holder to a receiver and trying it out. To do this, install the batteries and the telescopic antenna, then plug in the output ea ble and connect the other end to the antenna inputs on the receiver. After that, you just select the required band (A, B, C or D), tune in continued next page JANUARY 1990 21 Silicon Chip BACK COPIES February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Door Minder Alarm; Low Ohms Adaptor for Multimeters; Line Isolation Unit f,or Phone Patch; Electronics In The Jaguar XJ40; Easy Tips on Headphone Repair. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life for Radio-Cassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle for Model Railroads, Pt. 1 ; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players; What is Negative Feedback, Pt. 1 ; Mobile Antennas for the VHF & UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm; Walkaround Throttle for Model Railroads, Pt.2; Designing and Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. June 1988: Stereo Control Preamplifier (uses LM833), Pt.1; Breakerless Ignition For Cars Using Hall Effect Pickups; MegaFast Nicad Battery Charger; Automatic Light Controller Uses PIR Detector; RF Sniffer Probe & Preamplifier; What is Negative Feedback, Pt.2. July 1988: Stereo Control Preamplifier, Pt.2; Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source for Amplifier Headroom Testing; National Semiconductor LM833 Op Amp Data; What is Negative Feedback, Pt.3. August 1988: Building a Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter (uses OP-27), Pt.1; Discolight Light Show, Pt.2; Getting the Most Out of Nicad Batteries; Data on Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Switchmode Charger for 1 2V Gel Batteries; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2 ; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM12 150W Op Amp Data & Application; What is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (uses Rohm BA 1 404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting a CB Radio To The 28MHz Band; Electronics & Brock's BMW Blaster; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding a Headset To the Speakerphone; How To Quieten the Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs). Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Receivers; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter for Computers; Ultrasonic Proximity Detector for Cars; Simple Computer Sound Repeater; 1 20W PA Amplifier (With Balanced Inputs) Pt.1; How to Service Car Cassette Players; The Goalkeeper Gatling Gun; Massive Diesel Electrics In the USA. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways (uses LM3909); Build a Simple VHF FM Monitor (uses MC3362), Pt 1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board , Pt.1 ; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor for CD Players; Map Reader for Trip Calculations ; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics for Everyone - Resistors. Use this handy form to order your back copies 11111\ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + ---7 Please send me a back issue for: 1- 1 May 1 988 rI October 1 988 n n June 1 988 November 1 988 I I March 1 989 1- l April 1 989 I i August 1989 □ September 1 989 □ February 1 988 □ March 1 988 □ D July 1988 D August 1 988 D September 1 988 □ December 1 988 D January 1989 □ □ May 1989 □ June D October 1989 February 1 989 □ July 1989 1989 □ November April 1 988 1 989 D December 1989 Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my □ Bankcard □ Visa Card □ MasterCard Signature _ _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date _ __,__ _ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Street_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I Suburb/ town _ _ _ _ _ _ _ _ _ _ _ _ Postcode____ Price: $A5 .00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 OR FAX: (02) 982 9553 X I ~--------------------------------------~22 SILICON CHIP April 1989: Auxiliary Brake Light Flasher; Electronics for Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; Led Message Board, Pt.2; Fluke's New 80-Series Multimeters. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt .3; Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; Led Message Board, Pt.3; Coherent CW - a New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (uses TGS81 2 Gas Sensor); Extension For the Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics; Facts On the PhaxSwitch - Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7 -day Programmable Timer; Introduction to Stepper Motors; GaAsFet Preamplifier For the 2-Metre Band; Modern 3-Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (uses MC13024 and TX7376P) Pt.1; Alarm -Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089); Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (uses LMC669); A Guide to Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (uses BA 1404 and TDA?000) Pt. 1; GaAsFet Preamplifier for Amateur TV; 1 Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc in the PC; A Look at Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data & Applications; Install a Clock Card In Your PC; Index to Volume 2. Active antenna for shortwave listening Because it can tune out noise, the active antenna can outperform a longwire antenna. It can he used with virtually any shortwave receiver. the wanted station on the receiver, and adjust the tuning control on the active antenna for best signal. You should do this with the toggle switch S2 in the " - 20dB" position to make the signal peak more obvious. S2 is then switched to the "ON" position to maximise signal strength. If overloading now occurs due to excessive signal strength, return S2 to the " - 20dB" position. Finally, don't forget to switch the unit off when it is not in use to conserve the battery. The current con- The metal weight is affixed to the case lid to provide stability. sumption when the unit is on is only about 6mA so battery life should be around 200 hours_ ~ Where to buy the kit A kit of parts for this project is available from Jiloa Pty Ltd. This kit includes all parts and is supplied with a pre-drilled case and a silkscreened front panel. Prices are as follows: Complete kit of parts ............................................ $59.00 (incl. p&p) Fully built & tested ....................................................... ..... $11 9. 00 Optional carry case ..... ...................... .................... ...... $1 0. 00 extra Payment may be made by cheque or credit card number (Bankcard, Mastercard, Visa) with mail order, or by quoting credit card number for telephone order. Send your order to: Jiloa Pty Ltd, Technikit Division, PO Box 73, Glenhuntly, Victoria 3163. Phone (03) 571 6303. Note: copyright of the PCB artwork associated with this project is owned by Jiloa Pty Ltd. ]ANUARY1990 23 Mix and Match, and grab Special Offer!! 14" EGA MONITOR +EGA CARD CATACMEGA CAT VCEGA VGA MONITOR + VGA CARD CATACVGA Full analog VGA monitor, compatible with all VGA graphics cards. It is able to display up to 640 x 480 pixels in up to 256,000 colours . It features a 0.31 mm dot pitch tube with anti-reflective coating plus a tilt and swivel stand. MINI TOWER CASE WITH 200W POWER SUPPLY BABY AT CASE + POWER SUPPLY CAT CAATBBP CATCATBP Only$875 Normally $1, 148 SAVE$273 MULTISYNC MONITOR + EGA CARD CATACMM CATVCEGA The ACMEGA is a full EGA colour monitor, providing both text and graphics display with all EGA and EGA compatible graphics cards. It features a 0.31mm dot pitch tube with anti-reflective coating A tilt and swivel stand is provided. The ACMM is a multi-scanning full colour monitor, compatible with all video standards, providing both text and graphics display with all EGA and VGA systems as well as being able to work to a resolution of 800 x 600 pixels with a suitably configured VGA graphics card and driver software. Only $875 Normally $1,148 The Mini Tower case houses a rugged PC/AT/386 power supply, room for the mother board and up to 8 expansion cards, as well as 5 disk drives . Price including power supply. SAVE $46 ONLY$249 286HS HALFSIZE MOTHERBOARD CATMB2B6HS1 SAVE$273 MULTISYNC MONITOR + VGA CARD SPECIAL PRICE Only $675 Normally $848 SAVE$173 EXTRA SPECIAL!!! DISK BOX WITH 100 DISKETTES Normally $95 NOW$59 The cards provide complete register level compatibility with the IBM Video Graphics Array standard (VGA} , while being backwards com patible with EGA, CGA and Hercules Graphics/MDA monochrome standards. The VC1024 is fitted with an additional 256K of display memory for up to 1024 x 768 pixel resolution. Normally $1,298 Only$995 SAVE$303 Includes a heavy duty200WAT power supply. LIMITED STOCK ONLY$175 NEW 200W II AT" Power supply with built-in battery. CAT ACMM CATVC0BOO OR CAT VC!024 This enhanced graphics adaptor i an Electronic Solutions excusive. It is designed to upgrade the graphics display of the IBM PC/XT/ AT and compatibles to a high resolution display This compact PC/AT case features a flip-top lid and facilities for expansion for up to 8 slot mother boards. The internal drive mounting tray will accept up to 3 half height 5¼ hard or floppy drives . LEDs and switches for ResetJTurbo/Power are rpvoided. A keylock and key are also provided. Dimensions are: 360mm(W) x 165mm(H} x 400mm(D} Compact and economical, the new BABY 286HS is the smallest system board ever made and features: • Powerful and reliable 286 CPU running at 12MHz O wait state using 100ns DRAM • Versatile DISC (Dynamic 1/0 Speed Control} feature with selectable 1/0 wait state to adapt standard 8MHz add-on cards Special offer while stocks last. 1meg RAM included. Only $695 No-one will pull the plug on you ever again! You now have a battery which will allow you approximately 8 minutes to save your current work and power down safely. Black-outs will not be a worry, you will have plenty of time to save work and it is especially good for networking. BE QUICK, LIMITED STOCK. No picture available at time of printing ONLY$495 RING NOW AND ASK FOR OUR NEW SUMMER CATALOGUE WITH ALL OUR PRODUCTS LISTED a bargain for Chrisbnas! !! HURRY! NEC 360K D~IVES MICRO CHANNEL HURRY!! CATMCA LIMITED STOCK NEC 1.2MB DRIVES CATDD1157C This dual standard high/low desnity drive features a brushless DC motor for high reliability. Head positioning via a steel band and stepper motor for high accuracy. Transfer rate is 500K bits/sec Track to track access:3mS Dual speed design enables reading of 48tpi and 96 tpi media. Recording method: FM/MFM Power consumption: + 12V/390mA (startup), 210mA (idle), +5V /460mA ONLY$159 NORMALLY $199 SAVE$40 The Amazing "all-in-one" AT motherboard ** 2 Megabyte (PS/2) Compatible PS/2 Memory Board CAT MCM 2 Dual Async Adaptor This memory board provides up to 2 Standard double sided/double density, featuring brushless DC motor design. Transfer rate is 250K bits/sec Track to track access: 3mS Power consumption: + 12V/390mA (startup), 210mA (idle), +5V/460mA ONLY$140 NORMALLY $175 SAVE$35 PURCHASE EITHER NEC DRIVE with a four floppy disk drive controller for our special price. ONLY$240 The'I'urboXT Motherboard CAT MB1600 CAT MB286AIO This card is fully compatible with IBM's dual async adaptor for the PS/2 models 50, 60 and 80. Includes two fully programmable serial ports with two serial asynchronous communications ports (using NS16550 to ensure full compatibility and best performance). The card is autoconfiguring. It supi:,orts the POS of the Micro Channel™ architecture. False-start bit detection and line break detection are built in. The adaptor provides an EIA RS-232C interface. Tuvo 9-pin D-shell connectors (male) are provided to attach peripheral devices. Great Value ONLY$349 megabytes of expansion memory on a PS/2 type computer system. The board uses 1MB DIP type DRAMs Full print spooling and virtual disk facilities are provided, as well as EMS (LIM) support. Ok RAM ONLY$349 ** 2/8 Megabyte PS/2 Memory Board , ,,_ .:, ,_.., ,..., ;,;- -:: ., ....":,,'.,., ,' ...., ., .... , J"' ..., "',' ~ ; ~ ... < ,>~ . ~ :~~;:, >,,~~ :,\:-~~~--~;, ,: CATMCMB This memory board provides up to 8 megabyte s of expansion memory on a PS/2 type computer system. Maximum capacity is 2 megabytes using 256K x 9 SIMMs and 8 megabytes using 1M x 9 SIMM DRAMs. Ok RAM FANTASTIC PRICE ONLY$599 * * NEWPRODUCT! * * Dunson XT/AT RAM CARD CATRS6 This is a 12MHz 0 wait-state PC 'AT' Computer - complete on the motherboard (minus a video card). With the "All in One", you can build up a complete AT, with power supply, case, drive, keyboard and graphics card for as little as $1298. See article in August Silicon Chip for full details. • Up to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips • Tuvo serial ports and one parallel port on-board. • On-board floppy drive disk controller for both 5¼" and 3½" drives. • All cables for ports and floppy drives included. ONLY$545 The MB1600 is an IBM PC/XT compatible motherboard. It measures only 8½" x 9". The board runs at 10 MHz or 4.77MHz, providing complete compatibility with the IBM standard. Eight 62 pin edge connectors are also mounted o the board. the 1/0 channel is bussed across the eight expansion slots. The heart of the MB1600 is an 80883 microprocessor. The system board supports both ROM/EPROM and R/W memory. It has space for 32K x 1 and BK x 1 of ROM or EPROM. A full 640K of high speed RAM can be fitted on the motherboard. SAVE$50 ONLY$99 with V20 chip $109 • High speed with 0 wait state • 6MB memory on board • LIM 4.0 compatib le • Configurable for PC/XT/ AT or 386 systems OK RAM ONLY$295 ••••••••••••••••••••••••••••••• i um Ir~fil~1¥.;r;~~ ! I I I ; I ■ I I I II • We accept: Bankcard, Mastercard & VISA mail orders our specialty. Freight on smaller items is now $9.00 + $2.50 P&P • All prices include sales tax • All products carry a 14 day money back guarantee (software excepted) • All products carry a full 3 month warranty • All cards come with full documentation • Ring for quantity discounts and tax free prices I Due to technical advances products we supply may in some cases ■ vary from those pictured. In all cases they are guaranteed to perform I to an equal or higher standard. I I I ; I ■ I I I II ■ ■ I I ••••••••••••••••••••••••••••••• Phone patch for radio amateurs This easy-to-build circuit will take the hassles out of phone patch operation. It features a VOX circuit for automatic transmit/receive switching and can be matched to virtually any transceiver that features an effective squelch control. By JOHN CLARKE & GREG SWAIN OK, so what's "phone patch'"? Well, the concept is really very simple. Basically, it's a technique that involves connecting a 2-way radio circuit to a telephone line to extend communications to a third party. This can be particularly useful in emergency situations when normal communications are disrupted or where it is not possible to establish a full radio link. To establish a phone patch 26 SILICON CHIP operation, a 2-way radio circuit is first established between two transceiver stations. One of these transceivers is linked (or patched) to the telephone lines via a suitable switching circuit. Once the radio circuit is established, it's simply a matter of dialling the required number and then switching over to link the remote transmitter to the person on the telephone. In effect, the transmitter connected to the telephone lines serves as a relay station. In one direction, it receives signals from the remote transmitter and couples these into the phone lines via its speaker output socket. In the other direction, it picks up the signal coming down the phone lines via its microphone socket and transmits to the remote transceiver. One way of setting up a phone patch circuit is to employ manual switching but that's clumsy and requires some skill on the part of the operator. What's needed is a circuit that will automatically switch the transceiver between receive and transmit in response to the voice signal coming down the line. The SILICON CHIP Phone Patch circuit provides this function. It is completely automatic in operation and provides the necessary interface between the transmitter and the phone lines. In use, the Phone Patch is connected between the microphone ,--------------------------------------, I ~-------------------. I ,-------------------. I MC34018 I -----. j TRANSMIT BUFFER - . . : : . i - - - - - - - - - - . 1 TRANSMIT I I I I OUTPUT I ATTENUATOR I .---- I I --- --13 j I I ----. ---- -....L.- ,-----___,'--....--.;,...., SIDETONE NETWORK ATTENUATOR __-+--I TRANSMIT/ RECEIVE CONTROL COMPARATOR SIGNAL/NOISE DETECTOR Jj j j RECEIVE BUFFER I --- INPUT 1----...n.--1 15 1 I I I LINE ISOLATION UNIT LrJtr~R I MONITOR j LOUOSPEAKER '- - ---51---, 16 REGULATOR - ~'-+-BV....,_-I REGULATOR SPEAKER AMPLIFIER I I I 19 I 23 24 I I ~~~rr~: ~------ ------7 VR2 MICROPHONE LEVEL VR1 I I ~-----.J I I PHONE PATCH CIRCUITRY I I 1-----------------------~ 1 I 0-012VAC POWER I PLUG I I 26 RECEIVE IDLE CONTROL I I RECTIFIER L__ _J-----{? PACK ~mp~iLJE I I TRANSCEIVER S2bl C======:::::::!-~-...1 I MICROPHONE SOCKET L_ - - - - I ,...__ _ _ 1 ---1---e - - __ J Fig.1: most of the work in the Phone Patch circuit is performed by an MC34018 speakerphone IC. The VOX circuit triggers in response to speech coming down the phone line and simulates the PTT switch on the microphone. socket and the loudspeaker socket of the transceiver. It is then coupled to the phone lines via a line isolation unit (LIU). There are just four front panel controls: a Monitor control, a Microphone Gain control, a Mic/Patch switch and a Power switch. Also on the front panel is a microphone socket. This accepts the transceiver's PTT switch and microphone while an output lead from the Phone Patch now plugs into the transceiver's microphone socket. The Mic/Patch switch connects either the Phone Patch circuit or the hand-held microphone to the transceiver. This is a particularly useful feature because it allows the operator to transfer between phone patch operation and 2-way radio operation at the flick of a switch. It eliminates the need to unplug the phone patch circuit and then plug in the microphone, or vice versa, in order to switch from one mode to the other. The Monitor control is used to adjust the volume of an internal monitor loudspeaker. This feature allows the patch operator to monitor the 2-way conversation so that he knows when to terminate the call. It also allows him to keep track of the conversation so that he can talk to either party if necessary. Line isolation unit Because the Phone Patch is powered from the mains (via a 12V AC plugpack supply), it must be connected to the telephone lines via a Telecom-approved line isolation unit (LIU). A suitable LIU was described in the February 1988 issue of SILICON CHIP but you can also now purchase a commercial unit from Altronics (see photograph). On no account should you at- tempt to couple the Phone Patch circuit directly to the telephone lines. That would be dangerous and illegal. The LIU is there to isolate the phone lines from dangerous voltages and is a necessary part of phone patch operation. It's easy to connect up the LIU it's simply plugged into a telephone double adaptor socket in parallel with the existing phone. The connections to the Phone Patch circuit are then made via banana plugs and sockets (SILICON CHIP version only). After the call has been made, the LIU is switched into circuit and holds the line in the looped condition, thus allowing the telephone to be hung up. Speakerphone IC The SILICON CHIP phone patch circuit is based on the Motorola MC34018 speakerphone IC. We first used this chip in the Speakerphone project described in the September 1988 issue. Its use in this latest role was suggested by Ron Kilgour, VK3BDM, who built a prototype and submitted the circuit JANUARY 1990 27 The Phone Patch circuit is built into a standard plastic instrument case. The Mic/Patch switch connects either the Phone Patch circuit or the external microphone to the transceiver input. to us. We subsequently developed our own version based on his suggestion but with a number of modifications to make the unit easier to build. In fact, the MC34018 is ideal for phone patch operation. Because it is a voice-switched simplex system, it eliminates the need for a hybrid transformer. And whereas the latter is so critical to adjust that it frequently proves ineffective, the MC34018 suffers no such problems. So a major phone patch problem is overcome. Inside the MC34018 are all the necessary amplifiers, attenuators and control functions necessary to produce a high quality hands-free telephone. It includes a microphone preamplifier (not used here), a small power amplifier for the loudspeaker, transmit and receive attenuators, a background noise monitoring system and automatic gain controls for the transmit and receive sound levels. In operation, the MC34018 compares the transmit and receive signals to determine which is stronger and then switches into that mode. Normally, it operates in the receive mode but quickly switches to transmit mode when it receives a strong enough speech signal. Block diagram Fig.1 is a block diagram showing the functions performed by the 28 SILICON CHIP MC34018 IC, together with the additional functions needed for a complete phone patch circuit. At the bottom left of Fig.1 is the transceiver. This is connected into circuit between the Transmit Attenuator and Receive Attenuator blocks in the MC34018. The telephone, on the righthand side of the circuit, is connected to the phone patch circuit via the line isolation unit. Switch S2 is the Mic/Patch switch referred to earlier. In the Patch position, it switches the output of the Receive Attenuator (pin 26) and a VOX [voice operated switch) circuit to the microphone socket of the transmitter. When speech signals are received from the telephone line, the VOX circuit triggers and closes a relay. This simulates the action of the PTT (press-to-talk) switch on the microphone, and thus places the transceiver in transmit mode. When the party on the telephone stops talking, the VOX switches off and the transceiver goes into receive mode. Any signals picked up by the transceiver are then fed into the transmit attenuator (pin 3) of the MC34018. The circuit Fig.2 shows the complete circuit details of the Phone Patch. Let's start with the signal from the transceiver's loudspeaker socket. This is coupled to the transmit at- tenuator (pin 3, TXI) and also to the Signal/Noise Detector (pin 13, XDI). The Signal/Noise Detector (see Fig .1) discriminates between speech signals and background noise. If the signal on the transceiver's output is speech, a logic signal is fed to the Transmit Attenuator which then passes the speech signal to the transmit output at pin 4 (TXO). At this point, another logic signal becomes involved. The Transmit Level Detector (pin 5, TLI) monitors the Transmit Output at pin 4 (via Ql) and its output signal is fed to the Transmit/Receive Comparator. This controls whether the circuit is switched into the transmit or receive mode. When the Transmit Attenuator is at maximum gain (ie, when speech is passing through), the Receive Attenuator is at maximum attenuation (ie, fully off). Conversely, if only noise is present at the transceiver's output, the MC34018 will be in the receive mode. The Transmit and Receive Attenuators also take care of differences in voice levels. They provide plenty of gain for people who speak softly but prevent people who shout from overloading the system. The Transmit Output signal at pin 4 is fed to filter and buffer stages consisting of Ql, Q2 and Q3. Ql is a high-pass filter with unity gain. Its output signal is fed to the Transmit Level Detector at pin 5, as already mentioned, and also to the emitter of Q2 which operates as a grounded base stage. Q2's collector output couples directly to the base of Q3 which operates as a phase splitter. Q3's collector output drives the telephone line via the LIU while its emitter output provides a sidetone signal via a .068µF capacitor. In the other direction, signals from the telephone line are coupled to high pass filter stage Q4 via a Fig.2 (right): input signals from the transceiver are fed to the TXI (Transmit Attenuator) input of the MC34018, while signals coming down the telephone line are fed to the RXI (Receive Attenuator) input via buffer stage Q4. IC2c, IC2b, IC2a & Q5 form the VOX circuit. ► +BV TO LIU 220k POWER ,-----O~S1 .,_--+---<t-~>-'O~U-',f T 7808 t'I_N__..,__-+---, .01 GND +8V + 100 .01 470~ 1M +8V MONITOR VR2 10k LOG 18k .068 4.7 12 CP2 28 RAX 5 RTX TLO ALO 4.7k 30k 91 k 16 V+ RR RU TU SK0 IC1 MC34018 15 +4 47 ..__ _ _ _ _ _ _4'fTXO 80 SPEAKER RX0 26 TXI XDI 13 XDC 23 AGC 17 CPI 11 ACF 25 4.7 100k 0.1 vcc 20 VLC 24 01 + VB 21 + 0.1 4.3k RECEIVE 2.7k 0.1 +5.4V 2.7k 4.7k INPUT FROM TRANSCEIVER SPEAKER OUTPUT i 0.1 +2 .9V 47k 10k 47J- MICROPHONE INPUT 200k 200 k ~ 10J- 47+ 06 BC547 VB 470k MIC LEVEL VR1 20k 0 1i D7 1N4148 .,. 10k 14 .047 01+ PATCH * 01! .,. ,...._ __.,_ ..,_ +sv 0.1 RLA1 TO TRANSCEIVER MICROPHONE 01 1 SOCKET * * 01 + * 01! B 100k EOc A~K VIEWED FROM BELOW 2. 7k VR3 100k +BV 1t * CERAMIC •~oo, GN0 PHONE PATCH POWER A LED1 K A JANUARY1990 29 Background to Phone Patch Operation - By Philip Watson, VK2ZPW For amateur radio operators in Australia, phone patch operation has only been legal for the last two years This legal breakthrough was made as a result of efforts by the Wireless Institute of Australia and, specifically, by amateurs Sam Voron, VK2BVS; Jim Linton, VK3PC; Jack O'Shanassy, VK3SP; and Geoff Donnelly, VK2EGD. Geoff Donnelly, in particular, was responsible for designing a line isolation unit (LIU) which, properly cons'tructed, would meet Telecom approval if submitted for their inspection. Constructional details were published in "Amateur Radio" magazine for September and November 1987, and by Garry Cratt, VK2YBX, in SILICON CHIP for February 1988. Readers are referred to these articles. But this was only a first step. The line isolation unit merely provides the legal link between the amateur's equipment and the telephone line. It does not provide the phone patch facilities. This requires a separate unit. The basic phone patch problem is that we are trying to marry two different communication concepts: the duplex concept as represented by the telephone line, and the simplex concept as represented by the radio link. The term duplex means that the circuit can carry two speech channels, one in each direction, at the same time. While your friend is talking down the line to you, you can talk back and interrupt him if you feel so inclined - and he will hear you . Conversely, the simplex concept is a one-way-at-a-time arrangement. One party puts his transmitter on the air, says his piece, switches off his transmitter, switches on his receiver, and listens for the other party, who then goes through the same procedure. Clumsy though it sounds, this can provide rapid and accurate communication in the hands of experienced operators. In practice, of course, all the switching functions are normally performed by a single press-to-talk (PTT) switch on the microphone. Because part of the link is simplex (ie, via 2-way radio), this means that phone patch operation is also simplex. There's nothing that can be done about that - it just means that the person on the telephone must also adopt 2-way radio procedure. So how do we connect the two systems together? The most elementary approach is manual switching via a suitable line isolation unit. The telephone line is connected to a switch which directs it to either the transmitter (microphone) input or the receiver (speaker) output. The patch operator selects the setting, according to which party is due to talk, and also activates the transmitter as required. In spite of its elementary nature, this technique has been used extensively in the past, particularly by US amateurs when more elaborate systems were unable to cope. It's main disadvantage is that it requires some skill on the part of the Most of the parts are mounted on a single PCB to make construction really easy. The board is fastened to integral pillars inside the case using self-tapping screws. 15k0 resistor. Q4's emitter output couples into the Receive Attenuator (pin 27, RXI) and into the Receive Level Detector (pin 7, RLI) on the MC34018. Note that the sidetone signal from Q3 couples into the input of Q4, the receive input buffer. This signal is there to provide cancellation of the transmit signal which would otherwise be coupled into the Receive Input. As such, it is not really a sidetone circuit. Q3's collector output and the signals coming down the telephone line are also used to drive Monitor control VRZ via a 56k0 resistor. The signal from VRZ is then fed to the Speaker Amplifier input (pin 19, 30 SILICON CHIP operator. The next step, to make the system fully automatic, has two two basic requirements: (1 .) The transmitter must be equipped with a VOX (voice operated switch) system in order to sense speech from the telephone circuit and put itself on the air. Some commercial transmitters are already so equipped but if not, an external system must be added. (2.) Some means must be provided to isolate the receiver output from the transmitter input where they are both connected to the telephone line. If this is not done, a signal from the receiver that's intended for the telephone will also appear at the transmitter input. This would then trigger the VOX, put the transmitter on the air and shut down the receiver, thus circircumventing the intended operation . And this, as they say in the classics, "is the hard part" . Just how can the system be made to discriminate between the wanted telephone signal and the unwanted receiver signal? In fact, there is a circuit which SKI). The output from the amplifier appears at pin 15 (SKO) and drives the monitor speaker via a 47µF capacitor and 220 resistor. VOX circuit The output signal from the Receive Attenuator appears at pin 26 (RXO) and is fed to the microphone socket on the transceiver via S2a. This signal is also used to drive the VOX circuit via a 0. lµF capacitor. Op amps IC2c, IC2b and IC2a, together with Q5 and RLA 1, make u_µ,the VOX circuit. IC2c functions as a non-inverting amplifier with gain set by sensitivity control VR3. Its output is coupled to Schmitt trigger stage IC2b via a 3.3kfl resistor. Positive feedback around IC2b is provided by a 120kfl resistor which, in conjuction with the 3.3kfl resistor, sets the hysteresis. IC2b squares up the output from will do this, at least in theory. It is one developed by telephone engineers in the early days of trunk line systems, to enable a (valve) amplifier to amplify in both directions in a single telephone pair. It is called a hybrid circuit. Space does not permit a detailed description , but it is a balanced circuit, based on the Wheatstone bridge principle. And assuming a good balance, it can couple two separate signals into a third circuit, with minimum coupling between the two signals. Un fortunately , "assuming a good balance" is the operative phrase. This is relatively easy if all the circuits are purely resistive but practical telephone circuits also contain inductance and capacitance . And to make it harder, these values vary according to the length and nature of the telephone line. As a result , amateur systems based on a hybrid circuit often fail in practice; hence the previous reference to manual switching. This problem is overcome in this project by using the MC340 1 8 speakerphone chip which is a simplex system . IC2c and couples the resulting square wave signal to a charge pump circuit consisting of a 0. lµF capacitor, diodes D8 and D9, a lµF capacitor and a 100kfl resistor. When a speech signal is received, the lµF capacitor is rapidly charged towards the + 8V supply rail. Following the charge pump circuit is another Schmitt trigger stage based on IC2a. This stage compares the voltage across the lµF capacitor with the voltage at its inverting input as set by the VOX delay control VR4. When the voltage on pin 3 exceeds the voltage on pin 2, IC2a's (pin 1) output switches high. Bias for IC2a, 2b & 2c is derived from the VB output (pin 21) of the MC34018. This output will be at about + 2.9V. The 100kfl resistor on D9's anode provides a discharge path for the lµF capacitor to ensure that the VOX drops out when speech signals cease. IC2a's output drives transistor Q5. When the output is high (ie, when speech signals are received from the telephone line), Q5 turns on and activates the relay. This closes the relay contacts and activates the transmitter via S2b (ie, the relay contacts simulate the action of the PTT switch). Receive idle circuit Because the MC34018 compares the transmit and receive signals to determine which is stronger, a problem can arise if the telephone line is noisy. If this is the case, the MC34018 will favour (or even lock into) the receive mode and it will be difficult to get the chip to switch to transmit. This problem is solved here by adding a "receive idle" circuit consisting of Q6, Q7, IC2d and D7. Fig.1 shows how the receive idle circuit is connected to the MC34018. Q6 and Q7 are emitter followers and are connected between the Signal/ Noise Detector output (pin 23, XDC) and the Attenuator Control input (pin 24, VLC). IC2d and D7 form a peak detector circuit. Let's see how it works. The receive signal applied to RXI (pin 27) also drives the Signal/Noise Detector (pin 13, XDI) via a 0.lµF capacitor and 2.7kfl resistor. When voice signals in the receive mode exceed the background noise by 4.6dB, pin 23 switches high and turns Q6 on and Q7 off. This means that the voltage on the Attenuator Control input (pin 24) is set solely by VR1 (the Mic Gain pot). This in turn sets the signal level fed into the microphone socket from pin 26. When voice signals are no longer received from the party on the telephone, pin 23 decays to about 1.45V (½ VB). Emitter followers Q6 and Q7 are now both on, which means that the voltage on thA Attenuator Control input (pin 24) is now determined by the voltage on pin 23 (the Signal/Noise Detector output). This equalises the gains of the Transmit and Receive Attenuators and makes it easier for the circuit to switch from one mode to the other. The peak detector circuit formed by IC2d and D7 is required to JANUARY 1990 31 TO 12VAC PLUG PACK CORD GRIP GROMMET (:;. 0 MIC LEVEL TO TRANSCEIVER MICROPHONE SOCKET\ r7, CORD GRIP l GROMMET~ / FROM TRANSCEIVER SPEAKER OUTPUT Fig.3: here's how to assemble the PCB and install the external wiring. Take care to ensure correct orientation of polarised components and don't substitute for the 1 % resistors. CAPACITORS □ □ □ □ □ □ If you want to save money, you can build your own line isolation unit. This LIU was described in the February 1988 issue of SILICON CHIP. 32 SILICON CHIP No 9 3 2 9 2 1 Value 0 .1µF .068µF .047µF .01µF .0047µF .001 µF IEC EIA 100n 104 68n 683 47n 473 10n 103 4n7 472 1n0 102 disable the receive idle mode when constant level signals (eg, tones) are intentionally applied to the receive channel. Pin 14 of comparator IC2d is normally low but switches high when the incoming receive signal exceeds the comparator threshold PARTS LIST This line isolation unit is available for $99.50 from Altronics Pty Ltd. To use it with the Phone Patch, you must modify the plug wiring by moving the white lead from pin 4 to pin 2. A double-pole on/off switch should also be fitted in series with the leads to the telephone plug so that the unit can be easily switched out of circuit. (about 20mV). This charges the lOµF capacitor on pin 23 (XDC) via D7, thereby turning Q7 off and switching the MC34018 to the receive mode with gain set by VRl as before. Power for the circuit is derived from an external 12V AC plugpack transformer. Diodes Dl-D4 rectify the AC supply to produce a DC voltage which is then filtered by a 470µF capacitor and fed to a 7808 3-terminal regulator. The regulator output provides a + 8V rail and this is used to power the Phone Patch circuit. LED 1 and its associated lkO current limiting resistor provide power on/off indication. 1 PCB, code SC 12112891, 129 x 143mm 1 front panel artwork, 1 91 x 59mm 1 plastic instrument case, 205 x 159 x 69mm 1 57mm 80 loudspeaker 1 12V relay, SPOT (DSE Cat. S7120) 2 knobs 2 banana plugs 1 SPOT toggle switch 1 DPDT toggle switch 3 cord grip grommets 2 plastic P-clips 1 4-pin chassis mount microphone plug 1 4-pin microphone line plug 1 3 .5mm mono jack plug 1 1 2VAC 500mA plugpack transformer 26 PC stakes 1 piece of tinplate for shield, 82 x 73mm 2 metres of figure-8 cable 1 metre of 3-core or 4-core cable Semiconductors 1 MC34018 speakerphone IC (IC1) 1 LM324 quad op amp (IC2) 5 BC548 NPN transistors (01-04,06) 1 BC338 NPN transistor (05) 1 BC558 PNP transistor (07) 1 3mm red LED (LED 1) 6 1 N4002 1 A diodes (01 -06) 3 1 N4148 or 1 N914 diodes (07-09) 1 7808 3-terminal 8V regulator Capacitors 2 470µF 25VW PC electrolytic 1 5 4 2 4 9 3 2 4 5 2 1 1 OOµF 16VW PC electrolytic 4 7 µF 1 6VW PC electrolytic 1 OµF 16VW PC electrolytic 4. 7 µF 16VW PC electrolytic 1µF 16VW PC electrolytic 0.1 µF monolithic ceramic .068µF metallised polyester .04 7 µF metallised polyester .01 µF metallised polyester .01 µF ceramic .004 7 µF metallised polyester .001 µF metallised polyester Potentiometers 1 20k0 linear potentiometer 1 1 OkO log potentiometer 1 1 OOkO miniature vertical trimpot 1 1 OkO miniature vertical trimpot Resistors {0.25W, 5%) 1 2 2 4 1 2 1 3 2 1 1 2 5 1 1 1 1 10MO 2.2MO 1MO 470k0 220k0 200k0 1 % 120k0 100k0 91k0 1% 68k0 56k0 51 kO 1% 47k0 33k0 30k0 1% 27k0 24k0 1% 2 1 1 4 1 1 3 1 2 3 1 1 1 1 1 1 22k0 18k0 15k0 10k0 8 .2k0 6.8k0 4.7k0 4.3k0 1 % 3 .3k0 2.7k0 2.2k0 2k0 1% 1.2k0 1 kO 4700 220 Miscellaneous 200mm of hookup wire, tinned copper wire , solder, 6 selftapping screws to secure PCB. Construction Most of the circuit for the Phone Patch is mounted on a PCB measuring 129 x 143mm and coded SC 12112891. This is housed in a standard plastic instrument case measuring 205mm wide, 159mm deep and 68mm high. Before commencing assembly, check the PCB pattern carefully for possible defects. Any shorts between adjacent tracks or IC pads due to incomplete etching, or breaks in the copper pattern, are best corrected at this stage. Fig.3 shows the wiring details. Start by installing PC stakes at all external wiring points and to provide support for the metal shield (see photos). You will need 26 PC stakes in all (five for the shield). When all the PC stakes are in position, you can install the wire links and then move on to the rest of the components. Do not install ICl at this stage, however - that step comes later. It's a good idea to check all resistors with a digital multimeter before installing them on the PCB, as some of the colours can be difficult to judge. The accompanying table shows the codes used for the capacitor values. Make sure that all polarised components are correctly oriented when installing them on the PCB. These parts include the diodes, transistors, ICs, electrolytic capacitors and the 3-terminal regulator. The latter is installed with its metal tab nearest the edge of the PCB (ie, away from the relay). That's all we have space for this month. Next month, we'll complete construction and give a brief troubleshooting procedure. ~ JANUARY 1990 33 Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. +9V 16 100 + 16VW1 RESET I 4027 1k 16 0.1 ..l.. 14 3 CL 14 16 IC2b ii 2 R 4 R 15 "' 0.1 56k 12 1k LED1-30 IC4 4017 37 + 9V IC1 4017 ...L 13 CL ICJa ii 14 ii 2 +9V 13 _3•--+-~3 CL IC3b 3x1N4148 01 12 R _ IC2a CLf'-'13'--+--+--K--l----+---'¼-------------WIA.---½-I 14 1-------------------o .,. .,. Quiz game has light chasers for extra pizzazz Quiz games are not new and quite a few have been published in magazines over the years but those on TV such as "Sale of the Century" are becoming more elaborate. This circuit attempts to imitate those fancier games by incorporating a light chaser for each contestant. Inverters IC5a and IC5b are connected as an oscillator which runs at a high frequency to clock !Cl, a decade counter/divider which is connected as a 3-stage divider. Its outputs at pins 3, 2 and 4 successively go high. These outputs are connected to momentary contact pushbuttons S1, S2 and S3. When 34 SILICON CHIP one of these buttons is pushed by the contestant, it causes the associated flipflop to change state. For example, if button S1 is pushed, IC2b's Q-bar output will go high and turn on transistor Q4. This will allow the associated string of 10 light emitting diodes (LEDs) to be driven by counter/ divider IC4 which is clocked by IC5c and IC5d. At the same time, the high signal from IC2b will be fed to the clock input (pin 13) of IC2a, via diode D3. IC2a's Q-bar output then goes high and turns on transistor Ql to inhibit !Cl and thus prevent the other two pushbuttons, S2 and S3, from working. Once the contestant has answered the question, the reset switch can be pushed to reset any or all of the flipflops in IC2 and IC3 and to turn off any of the transistors Q 1 to Q4. This allows !Cl to scan the switches again and turns off the chaser lights. Daniel Garrard, Booleroo, SA. ($30) High and low boost for PA loudspeakers This circuit improves the sound quality of full range music signals when fed through heavy duty or musical instrument loudspeakers which are usually optimised for high mid-band sensitivity. It will not produce hifi performance nor can it increase the absolute acoustic power limits at low freqencies but at moderate power levels it will give better tonal balance. ICla is wired as a more or less Clipping indicator for stereo amplifiers bipolar output stages but should work with any amplifier with up to ± 100V supply rails. The circuit detects the onset of clipping and flashes a warning LED. It uses four comparators (ICla-lCld) to continuously compare the left and right channel outputs of the amplifier with the supply rails. The comparators are set to trigger if either output gets to within 6.2V of either rail - a threshold chosen because the amplifier at that point will either be clipping or so close that it doesn't matter. The open-collector outputs from the comparators are ORed together and thus pull the trigger input of 7555 timer IC2 low when clipping occurs. This IC is configured as a monostable with a duration of around a quarter of a second. Its output at pin 3 drives Ql which turns on and lights the LED during clipping transients. The left and right channel inputs can be taken from the junction of the emitter resistors before the output RLC network. If your amplifier uses Mosfet ouput transistors, the 6.2V zeners should be changed to 10V types. M.J.A. Hamel, Dunedin, NZ. ($30) One of the most common ways of destroying expensive speakers is to use them with an amplifier that has been driven into clipping by a high level signal source. Even if the speakers are rated well in excess of the amplifier's power, they can still be damaged by the high-level transients created by clipping. So how far can you crank up your amplifier? This clipping indicator circuit gives the answer. It was designed as an add-on for an existing amplifier with ZD1 L 6.2V 27k LEFT CHANNEL 27k 4.7k 4.7k 4.7k OV .,. 1Dk 82k 4.7k 14 IC2 7555 2.2 + -15V 27k 2D2 6.2V conventional Baxandall tone control stage set up for modest bass boost at low frequencies by virtue of the .068µF capacitor and the associated 22k!.1, 62k!J and 6.Bk!J resistors. Switch S1 allows optional modest treble boost. Two stages are required for a stereo version, and this can be done using an LF442 dual Fet-input op amp. If this low current National Semiconductor device is not obtainable, you could substitute a Texas TL062 or, if lower noise is desired, a TL072. Stephen Delft, Upper Hutt, NZ. ($25) Fig.2: ICla-ICld compare the left and right channel outputs with the supply rails. If either output gets to within 6.2V of either rail, the associated comparator output goes low and triggers IC2 to flash the LED. I I I 6.Bk .068 EXISTING CIRCUITRY 0.1 +9V 22 ,........-'\Mk-1-+ 22 t-=--=I + 10k -9V Fig.3: the circuit is based on ICla which is set up as a Baxandall tone control stage. S1 allows the treble boost to be switched out. JANUARY 1990 35 THE BEST PLACE TO SHOP! for Value and Selection. HIGH CAPACITY NICAD CHARGER • AAA, AA, C, D & 9 volt. 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ONLY s79ss With 60 watts capacity, low (24V) output voltage, 1.2 metre iron lead and 3 metre transformer lead, lightweight soldering pencil and special "closed loop" temperature control. Cat T-3000 s1&0 ECONOMY PENCIL BLOWTORCH Great for heatshrink work, silver solder, gold, silver, MINI TOOL KIT! 20 handy mini-tools in a handy plastic case. Contains brazing, glass work, etc. Fits easily in the pocket. Powered by butane gas (the same as they use in cigarette lighters, etc). Incredibly handy, incredible value. CatT-1380 5 open ended spanners (4.0-6.0mm_, 2 Phillips head screwdrivers, 3 Allen-Key drivers, 5 nut drivers (3.05.0mm), 5 flat screwdrivers and 1 tommy bar. CatT-4830 Only s19ss 15 WATT HOBBY IRON Mains powered, general purpose iron that's ideal for project building, service and other low-heat work. Rated at 15 watts it saves the hassle of cooked components in hobby work. Made for DSE by Weller so you can be assured of the quality. CatT-1310 s25ss -~~ 240 VOLT GENERAL PURPOSE Temperature control from 10 to 60 watts. Ideal for service people, handymen, technicians, etc. Cat T-1370 =- Another great iron from Scope. Rugged and reliable it's rated at 20 watts which makes it ideal as a general purpose iron for around 'the home, workshop, etc. Plugs straight into the mains and it's fitted with air cooled handle to make work more comfortable. Tips and elements are easy to replace so maintenance is a breeze. CatT-1620 p3ffL--3 UNIVERSAL TWEEZER SET A versatile tweezer set that's a must for the workshop or toolbox. 4 different 110mm tweezers with fine point blades, flat blades, curved tips and even reverse action. They're all housed in a handy plastic wallet. Cat T-4625 s1oss BARGAIN f!~t~rqe~~!~~t!!! ~ ~ ~ - ~ E ! ~ ~ ~nd makes repair or alterations much easier. Superb quality at a great low price. Cat T-2581 J t s5ss US ~e!!u~e9a~~~!!p !d!.~r~~!!Y ~~~!~!~ Ideal For Site Work! 3-IN-1 MODULAR TOOL • It's a DRILL • It's a SCREWDRIVER • It's a SOLDERING IRON • It's RECHARGEABLE CatT-5712 Justsgg screwdrivers with heavy duty handles and made from Chrome-Vanadium steel for longer life. Superbly engineered they're ideal for tradesman and handyman alike. Size Cat No. Price 4 X 100mm Flat T-6100 $7.95 6 X 150mm Flat T-6105 $9.95 8 x 220mm Flat T-6110 $15.95 3 x 150mm Flat T-6115 $9,95 75mm Phillips T-6120 $7.95 100mm Phillips T-6125 $9.95 With Period Counter! Talk about 'classy'! This has to be at the top of your list for workshop equipment. For the first time a truly intelligent frequency counter - PLUS a period counter - for hundreds of dollars less than meters that don't come close for accuracy or quality. Superbly constructed, with a range of unique features that are nothing less than astounding. It actually measures subsonic frequencies in fractions of a second with amazing accuracy. Measures right across the range from 0.1Hz to 1GHz. Check out these specifi cations .... INPUT CHARACTERISTICS CH.A (0.1Hz- 100MHz) -Frequency Range: DC couple 0.1Hz to 80MHz, AC couple 30Hz to 80MHz. Sensitivity: 15mVrms 0.1Hz to 50MHz, 25mVrms 50MHz to 80MHz. Coupling: AC/DC. Filter: Low Pass(100KHz, -3dB). Input Impedance: 1Mohm//40PF. Attenuator : X1, X20. Trig Mode: Auto or Manual. Period Range: 10nS to> 10S. INPUT CHARACTERISTICS CH.B (50MHz-1GHz) - Frequency Range: 50MHz to 1GHz. Sensitivity: 20mV to 650MHz, 55mV to 1GHz. Coupling: AC only. Input Impedance: 50 ohms. Max. Input: 3Vrms. Resolution : At least five digits at minimum gate time. Resolution depends on setting gate time control. TIMEBASE - Frequency: 10MHz. Aging Rate: < 1PPM/Month. Coefficient: < 10PPM, OC - 40 C, Accuracy: <50PPM. Line Var. : < 0.1PPM for line voltage +I- 10%. Gate Time : Continuously Variable from 60mS to 10S or 1 period of input signal, whichever is longer. High Performance - Low Cost! Digital & Bargraph! The DSt u-144U Digital Multimeter proves that great performance doesn't have to cost the earth. With features and specifications worthy of many digitals costing much more. Latest IC technology is used to achi eve the lowest possible component count - ensuring reliability, accuracy, and stability. It's durable and easy to handle. Includes fully shrouded probes for maximum safety. Requires only one 9V battery. • 15 ranges to 1OOOVDC, 500VAC, 200mA (AC/DC), 2M ohms • Diode & Transistor check. Cat Q-1 440 A fantastic all rounder for hobbyists, technician and service people alike. Both digital and bargraph displays gives you the best of both worlds. Large 30 position rotary dial for function and range selection makes it quick and easy to use. Superb features include automatic overload indication, high surg e voltage protection (1 .5KV -3KV) , capacitance measurement, diode and continuity, transistor hFE test and frequency measurement. RANGES: DCV: 200mV, 2V, 20V, 200V, 1000V. ACV: 200mV, 2V, 20, 200, 750. DC Current: 200uA, 2mA, 200mA, 20A. AC Current: 2mA, 200mA, 20A. Resist: 200, 2K, 20K, 2M, 20M (ohm). Diode Check: 2.8V <at> 1mA. Freq u. Count: 20KHz, 200Khz. Capacitance : 2000pF, 200nF, 20uF. Cat Q-1526 Bargain! $ ~ . ~ - TP.::-.:::::a 0 4995 Ideal For Sparks! 5 All the features an electrician needs. With a huge 21mm LCD display, pushbutton switches for mode and function selection, full range of measurements including AC/DC volts & Amps, resi stance, diode, continuity and frequency. Features audible continuity test, auto ranging on DC, over range indicator, data hold, etc. etc . Plus it's shock resi stant and full y sealed against water and dust. 179 Superb features, high accuracy and rugged reliability make this the pick of the bunch. A beautiful piece of equipment, it's ideal for the serious minded hobbyist or technician. The easy to read 15mm high contrast LCD display and data hold function makes service, repair and test work quick and easy. With capacitance measurement, diode testing, transistor measurement, frequency measurement, data hold, 4. 5 digit accuracy plus rugg ed construction for a trouble free life. RANGES: DCV: 200mV, 2V, 20, 200, 1000. ACV: 200mV, 2V, 20, 200, 750, DC Current: 200uA, 2mA, 200mA, 20A. AC Current: 2mA, 200mA, 20A. Resistance: 200, 2K, 20K. 200K, 2M, 20M (ohm). Frequency Counter: 20KHz, 200KHz. Capacitance: 2000pF, DCV: 400mV, 4, 40, 400 (9M ohm Imp). ACV: 400, 700. Current (AC/DC): 4mA. 40mA, 400mA, 2A, 20A. Resistance: 4K, 40K, 400K, 4M (ohm ). Frequency Counter: 4KHz, 20KHz (> 1%). Max volt. for freq.: 250V AC. Continuity: Buzzer (threshold approx 1.7K ohm). Cat Q-1524 s 129 Includes Battery Check! R A ongnt cnange ror me rooIoox! lnclu~es all the usual ranges, current to 10A and resi stance to 200megs... Plus a continuity checker with a fast 1OOms response time, a diode and transistor checker & battery checker (it tests under actual load conditions). Takes a single 9V battery (and tell s you if it's low) and comes compl ete with a flip down handle that doubles as a stand. RANGES : DCV: 0.2, 2, 20, 200, 1000V. CV: 0.2, 2, 20, 200, 650V. DC: 200uA, 2, 20, 200mA, 10A. AC : 200uA, 2, 20, 200mA, 10A. Res istance: 200, 2k, 20k, 200k, 2M, 20M, 200M. Transistor Check: Hfe. Diode Chec k: 1mA, 3.2V. Continuity: Buzzer. Battery Checks: 1.5V( <at> 200mA), 9V(<at> 6mA). Cat Q-1445 Save $5 ' It's Got The Loll RANGES: s199 200nF, 20uF. Cat Q-1528. Unbelievable Features and Value! s799s It's just astounding at the price! The DSE Dual Trace CRO with inbuilt component checker has features you'd be lucky to find on models which cost much more. It's a professional quality dual trace with outstanding performance, an economical price ... and looks to match! Features 20MHz bandwidth (-3dB), single or dual trace modes, dual trace in chopped or all. mode, 2 probe sets, inbuilt component checker - for capacitor, inductors, transistors, diodes, zeners, etc, and more! SPECIFICATIONS: DC-20MHz (-3dB), with < 17.5ms rise time and 3% overshoot. Deflection : 5mV/div to 5V/div in ~ • "' . ....... -- - · '.:"" - - ~· 10 ~librn"' '"" ' """ " DIC ,-,,-, ,-, ,, LI LI.LI + l-3"11mobaoo ~ II• o r.i5> , 0.1us/div to 2/div in calibrated steps. Triggering ~ ~ -~ - ~ modes: peak or normal from either/both channels • t2i. _,L<iQ · or external. Trigger sensitivity: 0.5V/div. Sweep ~ !!:~ ; delay:0.1us to10msi n 6 steps. • ' ii~&i•<!i~ ~-- e · CatQ-1260 Value! s995 A Must For The Toolbox! Value Plus! TRA T No physical connection is required (it works on inductive or capacitive coupling) so a dipper is ideal for working on live RF circuits. It's mechanically and electrically stable, has colored coded coils, headphone connection and it's battery operated. Plus, it comes at a great low price! Frequency Range: 1.5 to 250MHz. Crystal Oscillator: 1.5MHz. Modulation: Approx. 2kHz sine wave. Nominal accuracy 7% Cat0-1335 $ ONLY . ~-. ·rn· ~ ; ' ' ' ' t>ertect for photographers, video users, laboratories .. anywhere there's a need to measure light quickly and accurately. Measures up to 50,000 LUX over three range selections. It's battery operated (gives 150-200 hours continuous use), has low battery indicator, 13mm display and auto zero. Bargain priced as well' Cat Q-1400 Extremely handy and conveniently sized! With large, easy to read value selection so worki ng is less of a chore. Yo,u can select values from 5 ohms to 1M ohm in 36 steps using the most common divisions. Comes complete with insulated leads and crocodile clips for easy connection . Cat Q-141 O Just "Ii CJ) s179s ~ v&;12t£?' ~~ 139 ALL THE LATEST KITS! 2 Channel, 7 Day Our new Light Chaser is low in cost, easy to build, incredibly flexible and it's designed with safety in mind. With 6 chasing patterns, 8 speeds, an enhanced frontpanel monitor display and the ability to run lamps to a total of 2400 watts. It's been designed as a 'dedicated' chaser for the ultimate in safety. This also allows many more functions without getting into complex construction techniques. Comes complete (full form), right down to the last bolt! Cat K-3161 ~-------------,.. sgg - -- Design your own garden sprinkler system for about half the cost of commercial uriits! The Sprinkler Timer allows you to control up to 14 sectors (2 x 7). With the aid of any standard Distributor Tap and only one or two so lenoid valves you can have the healthiest garden in the street. Mains powered , the kit comes with case, pre-punched front panel, panel label and all components. Cat K-3588 DISTRIBUTOR TAPS & SOLENOIDS NOT SUPPLIED sg 9 0 Playmaster... The very latest in the highly successful Playmaster series. A 30/30 watt stereo amplifier that's easy to build, low in cost, provides all the essential features and offers excellent performance and superb noise and distortion specifications. Construction is made easy by mounting virtually all parts, including heatsinks, on one large PCB. Short form kit comes with 2 x TDA 1514 IC's, front and rear panels, transformer, PCB and instructions. Cat K-5100 sgg Your Phone Can Be A... Here's a way to add Hands-Free Speaker-Phone capabilities to your existing phone ... without spending a fortune. There's even a phones jack which is great ii a family member is a little hard of hearing. Comes complete with case, phone cable and plug, PLUS a telephone double adaptor - so there's nothing else to buy. Cat K-3100 Only s999s Small, lightweight, incredibly easy to tune and superb stereo sound! The Wide Band AM Stereo Radio is easy to build and requires no fancy tools or equipment. Comes complete with case, economy stereo headphones, prepunched front panel and all components. All you do is put it together, add 2 AA batteries and you 're away! Cat K-5200 s799s Incredibly Small! The FM Wireless Microphone is small enough to be inserted into a matchbox, can be tuned to operate at around 90MHz (On your FM receiver) , it's incredibly stable with extremely sensitive circuitry and relatively easy to bui ld. It's fantastic! Comes as a short form kit with components and PCB. Also includes batteries. Cat K-5006 s159s BEST SERVICE-BEST RANGE-BEST DEALS! IBM AT COMPATIBLE 80286 MOTHERBOARD Speed, power and versatility are yours with our 12MHz motherboard. You can build your own system or upgrade the old one. DRAM not included. LOOK .... • Expandable up to 4Mb • Selectable 8112MHz operation • Six 16-Bit and Two 8-Bit expansion slots. • Selectable RAM speed - 80 or 100 nanosecond • Selectable from Owait states on read operations (with 80 nanosecond RAM) • Socketed for 80287 Co-processor • Performance - 13.7 using Norton S.I. • Battery backed real time clock on board • AMI Bios ROM's included ;i\~:o~tpplied Save s•100 VGA GRAPHICS ADAPTOR More colours, higher resolution and more options with our VGA Graphics Adaptor! Perfect for AutoCAD, games, text, paint programs, graphics, charts, desktop publishing ... the lot! Fits into any IBM compatible (XT or AT) and comes with 256K RAM {expandable to 512K). Includes utilities which allow emulation of EGA, Hercules and CGA. All standard IBM VGA modes are supported plus 640 x 400 (256 colours) and 800 X 600 (16 colours). There are so many graphics modes available there's just no room to list them all! Comes with drivers and the exclusive Dick Smith Electronics 55 page manual. 8 Bit Version . Cat X-2018 16 Bit Version. Cat X-2019 New Low Price s399 s349 New Low Prices! Below Cost! HARD/FLOPPY DISK CONTROLLER Outstanding value! These can't last at this amazing low price. AT disk controller will handle 2 of hard and floppy disk drives. Comes complete with cables and full instructions. Cat X-2008 CONTROLS FOUR DISK DRIVES Allows you to install two internal and two external Exceptional Value! disk drives. 360K, 720K. 1.2Mb & 1.44Mb drives. Includes cables for internal drives and connection for external drives. Cat X-2024 s129 Limited Stocks Outstanding Buy! A FAX IN YOUR COMPUTER A smart space & time-saving idea! The Fax card simply slots into your PC and for a fraction of the cost of a separate fax machine, you get all the advantages. Comes complete with software. It runs as a resident program so it's always ready to receive a message. With memory for 200 fax numbers, automatic dial - in fact you can program it to dial out at any time when the phone charges are lowest - and more. A great device! Cat X-3302 Limited Stocks s599 Available in Sydney stores or through Mail Order only. 1.2Mb DISK DRIVES Easy to install in any IBM compatible! Great value half height floppy disk drives. Can be installed as an internal drive or externally {with optional case.) 5.25" drive for 1.2Mb floppies. Cat X-2200 Limited Stocks Unbelievable Buy! BIT BLITZER INTERNAL MODEM Saves Disks And Time! VIDEO TAPE HARD DRIVE BACK-UP Back-up your hard drive on video tape - there'll be no more worries about lost information. Allows you to store about 1meg of information per minute of tape - think of the disks you'll save! Comes with card and software. The card just slots into your PC and allows connection of video cables to most standard video recorders. You can even program it to save automatically. It's a fantastic idea 1 Cat X-3840 $ Limited Stocks 399 RS-232 MULTILINK ADAPTOR A complete in-line tester/adaptor which makes complex and time consuming Serial connections a breeze! Comes fitted with 25 pin male connector and 25 pin female connector. With jumper pads and wires, 24 in-line switches and 8 bicolour LED's for line monitoring. Cat X-2654 Outstanding value! You've now got the chance to pick up the amazing Bit Blitzer Internal Modem at an Outstanding LOW price. Features include 300/300 & 1200/ 1200baud rates, fully keyboard controllable, Hayes AT command set ... all the Bit Blitzer features. Cat X-3304 Don't Miss This One! ONLY$149 Limited Stocks Incredible Low Price! LASER 101 KEYBOARDS These won't last, so you'd better hurry! Fantastic 101 keyboards with 12 function keys, a great feel and the lowest price ever. Cat X-3819 Fantastic! Phone our Computer Hotllna 888 2002 ONLY s39es MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: N.S.W.: ARMIDALE: New England Electronics 711655 • BALLINA: Ballina Electronics 867022 • BOWRAL: F.A.H. Electrical 611861 • BROKEN HILL: Hobbies & Electronics 884098 • COFFS HARBOUR: Cotts Harbour Electronics 525684 • DENILIQUIN: Deni Electronics 813672 • DUBBO: Chris's Hi Fi 828711 • FORSTER: Forster Vil lage Electronics 545006 • GLEN INNES: John Sommerlad Electronics 323661 • GRAFTON: Repairs and Spares 421911 • GRIFFITH: Miatronics 624534 • INVERELL: lnverelt Electronics 221821 • LEETON: Leeton Audiotronics 532800 • LISMORE: Decro Electronic Services 214137 • .MOREE: Moree Electronics 523458 • MUDGEE: Headware 723895 • NARRABRI: Namoi Computer Service 923274 • NOWRA: Nowra Electronics 210722 • ORANGE: Central West Electronics 626491 • PARKES: Strad Music Centre 623366 • PORT MACQUARIE: Comdox 834574 • TAREE: Brads Electronics 526603 • WAGGA WAGGA: Phillips Electronics 216558 • VASS: Warmington Electrical 261116 VIC: BAIRNSDALE: LH & LM Crawford 525677 • MILOURA: Pullman Auto Pro 232882 • MORWELL: Morwell Electronics 346133 • SHEPPAATON: Andrew Guyatt Electronics 219497 • WARRNAMBOOL: Marrtronics 629870 QLD: AYR: Delta Electrix 831566 • BUNDABERG: Bob Elkin Electronics 721785 • MACKAY: Stevens Electronics 511723 • MARYBOROUGH: Keller Electronics 214559 TAS: BURNIE: Electronic City 314760 • DEVONPORT: A.I.Electronics 248322 SA: LOXTON: G & S Electrical 847495 • MT GAMBIER: Hutchesson's Communication Centre 250400 • PORT LINCOLN: Basshams TV & Computer World 822788 • WHYALLA: Eyre Electronics454764 WA: ALBANY: Micro Electronics 412077 • BUNBURY: Micro Electronics 216222 • Gll:RALOTON: Batavia Lighting & Electrical 211966 • KARRATHA: Daves Oscitronic 854836 • MANOURAH: Micro Electronics 5812206 SEMIS - GREAT RANGE & PRICES 74 SERIES TT Type No. 7490 74121 Cat No. Description Z-5210 Z-5260 Decade Counter Monostable Multivibrator Price Price Ea 10 up $1.65 $1.65 $1.60 $1.60 74LS SERIES TTL Type No. 74 LSOO 74LS01 74 LS02 74LS04 74 LS05 74LS08 74LS10 74 LS11 74LS13 74 LS14 74LS20 74LS21 74LS27 74LS30 74LS31 74LS32 74 LS37 74 LS47 74LS54 74LS73 74LS74 74 LS75 74LS83 74LS85 74LS86 74LS90 74LS95 74LS109 74LS1 23 74LS132 74LS138 74LS139 74LS153 74 LS157 74 LS165 74LS174 ',,J4L§J75 74LS190 74LS192 74LSl93 74LS196 74 LS221 74 LS240 74LS241 74 LS244 74LS245 74 LS367 74 LS373 74LS374 De•--;crip1ion Quad 2 input NAND gate Quad 2 input NANO gate, a/collector Quad 2 input NOR gate h ex inverter Hex inverter, open collector Quad 2 input AND gate Triple 3 input NANO gate Triple 3 input and gate DL 4in NANO Schmitt trigge r Hex Schmitt trig~er Du al 4 input NAN D gate Du al 4 input positive AND gate Triple 3 input NOR gate 8 input NAND gate Delay line Qu ad 2 input OR gate Quad NANO buffe r 7 seg ment dee butter 2 say ANO or inv Dual J-K flip flop Du al 0 -type edge trig. flip flop Qu ad bistable latch 4 bit full binary array 4 bit magnitude comparator Quad 2 input EXCLUSIVE-OR gate Decade counter 4 bit L-R shift register Dual JK flip flop Du al monostable multivibrator Qu ad 2 input NANO Schmitt Trigger ONE OF EIGHT Decoder Multiplexer ONE OF EIGHT Decoder multiplexer Du al 4 input multiplexer Qu ad 2 input mu ltiplexer Par Load Shift Register Hex D-type flip flop Quad D flip flop Up/down decade counter Sync dee up/down cir Bin sync up/down ctr Decade counter Dual mono multivibrators (S/trigge r) Octal buffer/ line driver Octal buffer/line driver Octal buffer/line driver Octal bus transce iver Hex bus driver & 3 staqe o/p Octal 3 stage latch Octal D-type flip flop Cat No Price Ea Price 10 up Z-4900 Z-4901 Z-4902 Z-4904 Z-4905 Z-4908 Z-4910 Z-491 2 Z-4913 Z-4914 Z-4920 Z-4924 Z-4927 Z-4930 Z-4931 Z-4932 Z-4937 z .4947 Z-4954 Z-4973 Z-4974 Z-4975 Z-4983 Z-4985 Z-4986 Z-4990 Z-4995 Z-5109 Z-5310 Z-5283 Z-5284 Z-5285 Z-5286 Z-5287 Z-5288 Z-5290 Z-5291 Z-4999 Z-5192 Z-5193 Z-5196 Z-5296 Z-5298 Z-5293 Z-5294 Z-5299 2 -5292 2-5295 2-5297 .75 .75 .75 .75 .85 .95 .85 .85 .85 .95 .95 $1.55 .95 1.05 $1.05 .95 .95 $1 .65 .95 $1.25 $1.15 $1.55 $2.25 $1 .45 $1 .25 $1 .45 $1.50 $1.25 $1 .65 $1 .95 $1.85 $1.55 $1.35 $1.75 $2.50 $1.40 $1.50 $2.35 $1.65 $2.25 $2.95 $2.25 $2.45 $2.85 $2.75 $2.75 $1.15 $2.45 $2 .45 .70 .70 .70 .70 .80 .90 .80 .80 .80 .90 .90 $1.50 .90 1.00 $1 .00 .90 .90 $1.60 .90 $1.20 $1.10 $1.50 $2.20 $1.40 $1.20 $1.40 $1.45 $1 .20 $1.60 $1 .90 $1.80 $1.50 $1.30 $1.70 $2.45 $1 .35 $1 .45 $2.30 $1.60 $2.20 $2.90 $2.20 $2.40 $2.80 $2.70 $2.70 $1 .10 $2.40 $2.40 74C/4000 SERIES CMOS Type No. 74COO 74C14 74C926 4001 4002 Description Quad 2 input NAND gate Hex Schmitt trigger 4 decade counter 7 seg. output Quad 2 input NOR gate Du al 4 input NOR gate Cat No. Price Ea Price 10 up 2-5410 Z-5413 2-5414 Z-5601 2-5602 $1.55 $1.50 $15.95 .80 .80 $1.50 $1 .45 $14.95 .75 .75 4007 4009 4011 4013 4015 4016 4017 4019 4020 4022 4023 4024 4025 4026 4027 4028 4029 4030 4040 4044 4046 4047 4049 4050 4051 4066 4069 4071 4081 4082 4093 40194 451 1 4616 4518 4520 4526 4528 45026/ 41342 45028/41344 Du al comp pair with inverte r Hex inverter buffer/lever shift Quad 2 input NANO Du al D edge triggered flip flop Du al 4 bit shift register Quad analog sw itch Decade counter/divider Quad AND/OR select gate 14 bit b inary cou nter Divide by 8 counte r Triple 3 input NAND gate 7 stage ripple counter Triple 3 input NOR gate Decade counter/? segment divider Dual J-K flip flop BCD to decimal decoder Preset up/dow n bi nary decade counter Qu ad EXCLUSIVE OR gate 12 stage ripple counter Quad R/S flip-flop Phase-locked-loop Monostable/Astable multivibrator Hex inverter/buffer Hex non inverting buffer 8 cha nnel analog multiplexer Quad analog switc h HEX inverter Quad 2 input OR gate Quad 2 input buffe red AND gate Dual 4 input AND gate Quad 2 input NAN D Schmitt trigger 4 bit bi-direct shift register BCD/7 segment decoder/driver/ latch Presettable up/down counter Dual BCD up counter Dual bi nary up cou nter 4 bit prog rammable down counter Dual Monostable Multivibrator Security En coder Security Decoder Z-5607 2-5609 2 -5611 Z-5613 2-561 5 2 -5616 2-5617 2-5619 2-5620 2 -5622 2 -5623 Z-5624 2-5625 Z-5626 Z-5627 2-5628 2-5629 Z-5630 2-5640 Z-5644 2-5646 2 -5647 Z-5649 Z-5650 Z-5651 Z-5666 Z-5669 2-5671 2 -5681 2-5682 2 -5693 2 -5694 2-5730 2-5738 Z-5740 Z-5742 2-5744 Z-5748 Z-542 5 Z-5430 $1.45 $1.45 $1.75 .90 $1.25 .70 .90 $1.50 $1.30 $1.30 $1.65 $1.75 $1.85 $1.65 $1.75 $1.05 $1.25 .95 $3.95 $1.15 $1.65 $1 .95 .95 $1.75 0.95 $1.15 .85 $3.75 .95 $1.55 $1.85 .80 $1.65 $1.65 $2.10 $2.40 $1.05 $1.05 $1.65 $1.05 .95 $1.35 .75 .95 $1.55 $1.75 $2.20 $2.50 $1.15 $ 1.15 $1.75 $1 .15 .80 .90 .75 $1.95 $2.15 $1.95 $9.95 $9.95 .85 .80 .85 $1.30 $3.80 $2.30 $2.80 $2.00 $1.85 $2.00 $1 .85 $9.45 $9.45 .85 .90 $1.40 $3.95 $2.45 $2.95 $2.15 74HC CMOS Cat No. Price Ea Price 10 up 74HCOO 74HC02 74HC04 74HC08 74HC11N 74HC14 74HC27 74HC30 74HC32 74HC74 74HC76 74HC85 74HC86 74HC123 74HC138 74HC1 39 74HC1 57 74HC1 65 74HC174 74HC221 74HC240 Quad 2 input NAND gate Quad 2 input NOR gate Hex inverter Quad 2 input AND gate Triple 3 input Hex Schmitt-Trigger Dual J-K flip-flop 8 input NANO gate Quad 2 input OR gate Dual D-type edge triggered flip-fl op Dual J-K master/slave flip-flop 4 bit magn itude comparator Quad 2 input EXCLUSIVE OR gate Dual re-triggerable monostable Expandable 3/ 8 decoder 1 of 8 decoder/ multiplexer Quad 2 input mu ltiplexer Par load 8 bit shift regi ste r Hex D-type flip-flop Dual mono multivibrators (S/trigger) Octal Buffer/line Driver 2-5800 2-5802 2 -5804 2-5808 2-5811 Z-5814 2-5827 2-5830 2-5832 Z-5874 Z-5876 Z-5885 Z-5886 Z-5910 Z-591 5 2-5920 Z-5925 Z-5930 2-5935 2-5940 Z-5945 .95 .95 .95 .95 .95 $1.50 .95 .95 .95 $1.10 $1.45 $2.25 $1.25 $2.90 $1.25 $1.55 $1.95 $2 .25 $2.25 $4.25 .95 .85 .85 .85 .85 .85 $1.40 .85 .85 .85 $1.00 $1.35 $2.15 $1 .15 $2.70 $1.15 $1.45 $1.85 $2 .05 $2.15 $4.05 .85 74HC244 74HC245 74HC367 Octal buffer/line driver Octal bus transceiver Hex bus d river & 3 state o/p 2-5950 Z-5955 Z-5960 $2.45 $3.50 $1.95 $2.35 $3.30 $1.85 Description Type No. Bulk Buy - And Save ill XPRESS Phone or Mail Order Service OUTSIDE SYDN EY - (LOCAL CA LL FEE) 008 22 6610 SYDNEY AND ENQUIRIES - 888 2105 Fax (02) 8051986 OR Write To OS XPRESS, PO Box 321 North Ryde NSW 2113 All major credit ca rds accepted. 0/Nite courier available. PHONES 24 HOUR DESPATCH OF ALL ORDERS DICK SMITH ELECTRONICS STORES • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Campbelltown (046) 27 2199 • Chatswood, Chase 411 1955 • Ch ullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle611896 • North Ryde878 3855 • Parramatta 689 2188 • Penrith (047 ) 32 3400 • Rai lway Square 211 3777 • Sydney City 267 9111 • Tamworth 661711 • Warringah Mall 905 0441 • Wollongong 28 3800 • ACT• Fyshwick 80 4944 • VIC• Ballarat 31 5433 • Belmont 43 8804 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg (03) 383 4455• Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray6892055 • Frankston 7839144 • Geelong 232 711 • Melbourne City 326 6088 • Ric hmond 428 1614 • Ri ngwood 879 5338 • Springvale 547 0522 •OLD • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Red bank 288 5599 • Rockhampton 27 9644 • Southport 32 9033 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 • SA • Adelaide City 2321200 • Beverley 347 1900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • Midland 250 1460 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 SECURITY AUDIO COMPUTERS The Largest Australian Electronics Retailer! 605wresAaossAusuaHa . A high quality audio oscillator: Pt.1 Just where do you go to obtain an oscillator which will put out high quality sine and square waves at up to 10 volts RMS and with 3-digit frequency resolution? Well look no further. This unit will do stirling service in any workshop or laboratory. By LEO SIMPSON Finding a good quality commercial oscillator these days is pretty hard, particularly if you want low distortion and high output. Sure, there are plenty of function generators which will cover the range from DC to daylight (eg, from a fraction of a Hertz to 10MHz or more) and there is no doubt that for many laboratory and workshop tasks, function generators are perfectly adequate. Besides their wide frequency range they are quick to stabilise in amplitude and they often have a digital readout so that you know the exact frequency. However function generators can 42 SILICON CHIP rarely do better than about 0.5% harmonic distortion and for many applications, particularly those involving measurements of loudspeakers, amplifiers and other audio equipment, 0.5% harmonic distortion is just not good enough. In addition, the harmonic distortion of function generators is generally quite "spiky" in nature (ie, high order harmonics) and therefore quite audible, particularly when working with loudspeakers at the lower frequencies. A reasonably high output voltage is also a relative rarity as far as many commercial sine/square wave oscillators are concerned. Many oscillators will put out a maximum of 3 volts but we wanted a lot more than that - 10 volts RMS was our target. Why? Well, for example, when testing the input overload capability of preamps you want 5 or 6 volts or more. Also on our wish list was good envelope stability and quick settling. Many low distortion oscillators have poor envelope stability and long settling times. Partly this is due to the use of a thermistor in the feedback loop of the oscillator and partly it is due to the use of a less than perfectly matched dual ganged potentiometer for frequency setting. Other desirable points for a high quality oscillator are ease and repeatability of frequency setting as well as a wide range output attenuator. Having outlined some of our wishes, let us now discuss the features of our new Audio Sine/ Square Oscillator. As can be seen from the photographs, the oscillator is hous- ed in a standard Horwood instrument case made from black Marvipla te and measuring 307mm wide, 236mm deep [including handles) and 108mm high. On the front panel is a meter with three scales: O to lV, O to 3.16V and - 15dB to + ZdB. To the left of the meter are two BNC sockets which provide the main oscillator output and a sync output which can be connected to the sync input of an oscilloscope or to a digital frequency counter. Above the two BNC sockets is the main attenuator which varies the output in nine lOdB steps from 1 millivolt to 10 volts RMS. The attenuator also has a GND position [fully anticlockwise) which ensures that the oscillator output is fully off. This is handy when you want to remove the signal but you don't wish to disconnect the oscillator as, for example, when making signalto-noise ratio measurements. To the left of the BNC output sockets are two miniature toggle switches. One selects the sine or square wave modes while the other connects the case of the oscillator to mains earth or lets it float. Again, the ability to do this can be important in some measurement setups. Above the two toggle switches is a small knob which provides a variable output control. This allows the output to be reduced to zero on any position of the main attenuator. Frequency setting The four remaining knobs on the front panel are for frequency setting. One is the 4-position Range switch while the other three set the frequency with 3-digit resolution. Most equivalent audio oscillators use a dual gang potentiometer as a variable frequency control which has the advantage of being continuously variable but there are a number of disadvantages. First, the frequencies are inevitably cramped at one end of rotation. Second, the frequency scale must be carefully designed to suit a particular dual pot. If the pot varies at all in its overall resistance and its electrical rotation, the frequency scale is likely to be quite inaccurate. SPECIFICATIONS Frequency Range Frequency Resolution Frequency Accuracy Harmonic Distortion Squarewave Rise Time Squarewave Fall Time Output Level Output Impedance Load Impedance Protection Sync Output Sync Output Impedance Third, for lowest distortion, quick settling and best amplitude stability, the dual pot needs to be a high quality wirewound dual potentiometer with closely matched sections. Such a potentiometer is about as rare as a mint quality Ford Prefect - you just can't get 'em! Hence, we have gone for the more complicated but more readily available arrangement of three rotary switches for frequency setting. The switches give precise and accurate frequency setting, good envelope stability and contribute to the low distortion. We should note at this point though, that the multiwafer switches are expensive and a major part of the total oscillator cost. Also on the front panel is a red LED which functions as a power indicator. This is necessary to tell you that the oscillator is on because when the output is turned down, the meter will be indicating zero. The power switch is on the rear panel. It is there to keep all the internal mains wiring as far away as possible from the sensitive oscillator circuit and keep hum output to the absolute minimum. Specifications Most of the relevant perfor- 1 OHz to 109.9kHz in four ranges with 11 % overlap between ranges 3 digit Typically better than ±2% 20Hz (0.1% 1 OOHz (.02% 1kHz ( .0025% 10kHz ( .003% 20kHz ( .01 % 1 OOkHz ( .05% (all at 1 OV RMS) (30ns (20ns Continuously variable from 0-1 OV RMS in nine ranges 6000 (nominal) 6000 to infinity Short circuit protected 1 OV RMS sinewave 10k0 mance specifications are included in the panel accompanying this article. As you can see, the harmonic distortion figures are quite respectable although they are not extremely low. This is mainly as a result of the circuit not using a thermistor in the feedback loop for envelope stability. A thermistor could be used to give a better result but envelope stability would probably not be anywhere near as good. Apart from that reason, we have not used a thermistor because suitable units are now very expensive and at times they can be impossible to obtain. Some readers may wish that we had designed the oscillator to cover lower or higher frequencies. We have not done so for two reasons. First, we had to draw the line somewhere and increasing the frequency range would have required adding at least one more range. Second, operating an oscillator of this circuit configuration with a wider frequency range does not give particularly good distortion figures or good envelope stability a function generator is a better performer at very low and very high frequencies. Square wave rise and fall times JA NUA RY 1990 43 Cl Rl R2 THl R3 .,.. Fig.1: typical Wien bridge oscillator circuit. The thermistor (TH1) in the negative feedback path increases in resistance as it warms up and stabilises the output amplitude. Cl Rl R2 We '11 talk a bout these in some detail later. Before getting down to the nuts and bolts of the circuit operation, let us first explain how a Wien bridge oscillator works. Refer to Fig.1 which shows how a Wien bridge oscillator is usually connected. Fig.1 shows an operational amplifier with two feedback networks. The first network consists of resistor Rl and capacitor Cl in series from the output to the noninverting ( + ) input together with resistor R2 in parallel with capacitor C2 from the non-inverting input to the OV line. This network gives positive feedback from the output to the non-inverting input. The second feedback network consists of thermistor THl from the output to the inverting ( - ) input and then resistor R3 from the inverting input to the OV line (GND). This network provides negative feedback. ":' Pseudo resonance Fig.2: the thermistor can be eliminated by substituting an incandescent lamp and rearranging the feedback as shown here. are quoted at less than 30ns for the rise time and less than 20ns for the The network consisting of Rl, R2, Cl and C2 is known as a Wien network and it acts in a similar way to a tuned LC circuit. And just as a tuned LC circuit will give a resonance at a particular frequency then so does the Wien network give a "pseudo resonance". The frequency at which this pseudo resonance occurs is given by the formula: 1 Fo = 27!" jR1.R2.c1.c2 fall time. Verifying these figures can be difficult, depending on the CRO and probes used. To do it accurately, you need a CRO and probes with a bandwidth of at least 100MHz. The typical 20MHz CRO and its 10:1 probes are just not good enough. We used a 150MHz CRO and 250MHz probes. Circuit details Let's face it, the circuit is relatively complicated although it does have a number of elegant features. It is based on the conventional Wien bridge configuration but as noted above, it does not use a thermistor in the feedback loop for envelope stability. Instead, it uses one or two incandescent lamps. 44 SILICON CHIP -~;::::::::======= Now if Rl is made equal to R2 and Cl is made equal to C2, the formula is simplified to: F _ _1_ 0 - 27l"RC At this "resonance" frequency, the phase shift from output to input will be zero (or a multiple of 360°) and the transmission loss through the network is a minimum which is actually 3.0. Another way of saying this is that the gain is 0.33. Now for the system to oscillate with a steady amplitude, that loss of 0.33 via the positive feedback network must be exactly cancelled out. To achieve that, the negative feedback network must set the gain of the amplifier to precisely 3.0. When that happens, the circuit oscillates with a steady amplitude. In some books or magazine articles on Wien bridge oscillators you may see a reference to the "gain around the loop being equal to unity" if steady oscillation is to occur. This is correct but is not easy to understand. Think of it this way. The gain in the Wien RC network is 0.33. The gain from the noninverting input to the output is then equal to 3. If you multiply 0.33 by 3 the result is unity. Non-linear feedback element The problem in any Wien bridge circuit is how do you maintain the gain of the amplifier at exactly the right value? That is what the thermistor is there for. It has a negative temperature coefficient so that if its temperature rises, its resistance drops markedly. It works as follows . When the circuit first turns on, the thermistor will be cold and its resistance will be high. Therefore the negative feedback around the amplifier will be low and the oscillations in the circuit will build up rapidly. As the voltage at the output rises, current will pass through the thermistor and it will start to warm up. As it warms up, its resistance will drop and the negative feedback will increase. This means that the overall circuit gain will fall and so the speed at . which the oscillation is building up will be reduced. Eventually, the circuit will reach equilibrium and it will oscillate at a steady amplitude. The time which it takes to come to this steady state is the "settling time" . So we see that by using a nonlinear component such as a thermistor, we can stabilise the amplitude of oscillation in a Wien bridge circuit. Incandescent lamp But earlier we said that our circuit does not use a thermistor Fig.3 (right): the circuit uses a low► distortion amplifier (Q1-Q10) which oscillates due to the positive feedback components selected by switches S1-S4. 11.7k 1Bk// 33k 1.95k 3.9k// 3.9k 3.9k 1.17k 1.Bk// 3.3k 78011 1.1k// 2.7k 4151! 560!! 3250 560!!// 620!!// 1.6k 680!! 260!! 2.34k 300U// 2k 4.3k// SB A~ 5.1k D5 M1124 '-o-, ~2~4~V--~H-+------t ~A1C2V 240V ::) S1a 117k 180k// 330k 0 7.Bk 11k// 27k 26k 30k// 200k 4.15k 5.6k// 16k N ~~1-2v_-+----+---+---+---<t----+--ov 1000 35VW nfT7 0 .J: 1 25VW _ - 3.3k 100 15VW CASE S2a 1.17M 1.BM// 3.3M 390k 117k 18Dk// 330k 78k 110k// 270k 56k 41.5 k 56k// 160k 32.5k 62k// 68k 260k 300k// 2M 1N4004 S3a 0.68 15!! S4b 2.34k 4.3k// 5.1k S4c x1 ,10,0 3.25k 6.2 k// 6.8k * ADJUSTFOR 15mA QUIESCENT CURRENT ~1k q100 J. .006~ 0.68~06BI ,.~470pF // d_. 180pF , 10 ,100 4.15k 5.6k// 16k x1 5.6k 06 x1k 1xBC546 S4d 1.1k 2.2k 560!l -11v---...--➔--+-----------------➔--~--~ 780!! 1.1k// 1.7k 1.17k 1.Bk// 3.3k 1.95k J°.9k// 3.9k 10k 3.9k S1b SINE S3b SYNCcp 17k S5c 11.lk 18k// 33k SOUARE +21V s: OUTPUT 10k 014 BC639 470!! 012 51 O~! BC640 ..--1--+-~t--t 8 2.1 BP 160U 51\l 161 1 10k 7.511 -11v---<t----..,__ __ LM317 LM337 ~ 0 0 0 <at>J Ill BC546.548. 556,557 B EOc BC639 ,640 C aOE o<at>s 01 51U FLOAT~ VIEWED FROM BELOW ••~• ,ru~oo, OUT IN SG O m GND9 -d:,. Sl - 16!.? lflrl CASE AUDIO SINE/SQUARE OSCILLATOR JANUARY 1990 45 lkHz sine wave at maximum output: 0.2ms/div and 5V/div. Square wave rise time is less than 30ns; shown at 20ns/div. Square wave fall time is less than 20ns; shown at 20ns/div. 20V RMS square wave output at 100kHz. Note the lack of ringing. 20V RMS square wave output at lkHz. It has even less ringing. 20V RMS square wave output at 100Hz. Note lack of droop. because suitable units [such as the well known R53) are expensive and can be hard to get. So our circuit is a variation of Fig.1 and is shown in Fig.2. Here, the thermistor has been replaced by fixed resistor R3 and resistor R3 in Fig.1 has been replaced by incandescent lamp Ll. Incandescent lamps are also nonlinear but they have a positive temperature coefficient. When their temperature rises their resistance increases sharply. By arranging the negative feedback as shown in Fig.2, the incandescent lamp achieves the same result as in Fig.1. Oscillation is steady after an initial settling time. By designing an amplifier which has a very low distortion to begin with and then by carefully selecting a non-linear feedback element, in our case an incandescent lamp, the oscillator will operate with very low distortion. So the complete circuit of the oscillator is essentially an amplifier with very low distortion which is then provided with suitable feedback components around it to make it oscillate. resistors using Slb, S2b and S3b. These are equivalent to R2 in Fig.1 [or Fig.2). Circuit details Switch banks Now have a look at the complete circuit. Before we go into detail, let's just locate the main sections of the circuit. At the top righthand corner is the power supply which puts out ± 22 volts. Then below the power supply is the low distortion amplifier which uses BD139 and BD140 transistors (Q9 and QlO) in the output stage. To the left of the power section is a group of three switched resistance banks, using switch sections Sla, S2a and S3a. This is equivalent to Rl in Fig.1. Below the switched resistance bank are a number of ganged switch sections, S4a, S4b, S4c and S4d, which select capacitors. These are equivalent to Cl and C2 in Fig.1. Finally, to the left and slightly below the four section switch S4 is another group of three switched It won't be apparent just what is happening in the switch banks when you first look at them so we'll fill in some of the details. First look at the three resistor strings associated with Sla, Slb and Slc. Each switch section is wired as a variable resistor and the three sections are in parallel. Let's now assume that the frequency multiplier switch S4 is set to the "xl" range. Now any frequency combination selected by the frequency range switches [ie. Sl, S2 and S3) will be multiplied by one and we can select any frequency between lOHz and 109.9Hz. The lowest resistance string, at the top, is the most significant digit in the frequency, and in this case, sets the frequency in multiples of 10; ie. lOHz, 20Hz, 30Hz, 40Hz, 50Hz and so on up to lO0Hz. 46 SILICON CHIP PARTS LIST 1 Horwood instrument case , 305 x 1 02 x 203mm 1 24V centre-tapped transformer (Altronics Cat. M-7124) 1 240VAC 15A plastic bodied SPOT toggle switch (Altronics Cat. S-3220) 1 SPOT miniature toggle switch 1 3POT miniature toggle switch (Jaycar Cat. ST-0505) 1 single pole 12-position rotary switch 3 2-pole 12 position rotary switches with screen plate (from Farnell Electronics, see text) 1 4-pole 6-position rotary switch (from Farnell Electronics, see text) 4 21 mm collet knobs and caps for 6mm shafts 1 21 mm collet knob and cap for 6.4mm shaft 1 1 5mm collet knob and cap for 6.4mm shaft 2 lamps , 28V 40mA (Farnell Electronics Cat. CM 7 3 7 4; see text) 2 insulated BNC panel sockets 1 1 00µ,A MU-65 panel meter 31 1 .2mm PCB pins 4 6mm high spacers 4 10mm spacers tapped 3mm 5 3 x 1 2mm screws 8 3 x 6mm screws 5 3mm nuts 1 solder lug 1 3-core mains cord and plug 1 cordgrip grommet 1 metre 250VAC rated hookup wire 3 metres hook-up wire 4 stick-on rubber feet Printed circuit boards 1 oscillator board , code 04101901, 207 x 93mm The second resistance string, just below, is ten times higher in value and sets the frequency in units. For example, if S1 is set to 60Hz, S2 enables the frequency to be set anywhere from 60Hz to 69Hz. The third resistance string, is ten times higher again in value, and sets the frequency in multiples of 0.1Hz. So if S1 and S2 have been set for 65Hz, S3 enables the frequency 1 power supply board, code 04 101902, 108 x 64mm Semiconductors 2 1 N41 48 silicon diodes (01 ,02) 2 OA90 germanium diodes (03,04) 2 1 N4002 rectifier diodes (05,06) 3 BC557 PNP transistors (Q1 ,Q2 ,Q3) 2 BC556 PNP transistors (Q4,Q5) 2 BC546 NPN transistors (Q6,Q7) 1 BC548 NPN transistor (Q8) 1 BD139 NPN transistor (Q9) 1 BD140 PNP transistor (Q10) 1 VN 1OKM N-channel Mosfet (Q11) 2 BC640 PNP transistors (Q12,Q15) 2 BC639 NPN transistors (Q13,Q14) 1 7 4C14 hex Schmitt inverter (IC1) 1 LM78L 12 positive regulator 1 LM31 7T variable positive regulator 1 LM337T variable negative regulator 1 5mm red LED (LED 1 ) Capacitors 2 1 OOOµF 35VW PC electrolytic 1 330µF 25VW PC electrolytic 4 1OOµf 25VW PC electrolytic 1 1 OOµF 16VW PC electrolytic 2 1 OµF 25VW PC electrolytic 1 2.2µF 50VW BP electrolytic 6 0 .1 µF 63V polyester 1 22pF 50V ceramic Close tolerance capacitors 2 0 .68µF 63V 2% polycarbonate (Mayer Kreig NSR 680 VG 63) to be set anywhere from 65Hz to 65.9Hz. Note that many of the resistance values on S1a, S2a and S3a are parallel combinations of two resistors. This was necessary to give the precise values we needed. Note also that exactly the same resistor values are used with S1a, S1b and S1c. This is to be expected since Slb is ganged with Sla, S2b is 2 .068µF 1 OOV 1 % polypropylene (Mayer Kreig MKP 1837-368-013) 2 .0068µ,F 63V 2 .5% polypropylene (Mayer Kreig KP 1830-268-063) 2 470pF polystyrene 2% 2 180pF polystyrene 2% Potentiometers 1 1 kO linear Trimpots 1 1OkO horizontal mount 1 5k0 horizontal mount 1 1 kO horizontal mount 1 5000 horizontal mount 1 2000 horizontal mount Resistors (¼W, 1 %) 2 3 .3MO 6 3.9k0 2 2MO 4 3.3k0 2 1.8MO 1 3.3k0 ½W, 5% 6 39 0k0 2 2 .7k0 4 330k0 3 2 .2k0 2 2k0 2 300k0 2 270k0 2 1.8k0 2 1.6k0 2 200k0 4 180k0 2 1 .1 kO 2 160k0 2 1 kO 2 11 OkO 3 6800 2 6200 2 68k0 2 62k0 5 5600 2 5100 4 56k0 1 4700 6 39k0 2 3000 4 33k0 2 30k0 2 2000 1 1800 1W, 5% 3 27k0 4 1600 4 18k0 2 1500 2 16k0 1 1000 2 11 kO 1 820 7 10k0 2 510 1 8.2k0 2 160 3 6 .8k0 2 150 2 6.2k0 2 7 .50 5 5 .6k0 2 6 .80 2 5.1 kO 2 4 .3k0 ganged with S2a and S3b is ganged with S3a. Oscillator amplifier It is often said that any amplifier can be an oscillator and any oscillator can be an amplifier - it is just a matter of how the feedback works. In our case, we start with a low distortion amplifier and then make it oscillate by connecting the JANUARY 1990 47 The oscillator is built into a metal case. There are two PCB assemblies: an oscillator board and a power supply board. Wien network around it. The amplifier is very similar to some of the power amplifiers we have described in the past except that the output stage does not use high current power transistors. Transistors Q2 and Q3 form a differential input stage with their operating current set by constant current stage Ql which is referenced by diodes Dl and DZ. The outputs of the first differential stage are fed to another differential amplifier stage consisting of Q6 and Q7. These two transistors have their operating currents set by the "current mirror" consisting of Q4 (which is connected as a diode) and Q5. Q7 drives the complementary emitter follower output- stage consisting of Q9 and QlO. These two transistors operate in class AB with a collector current of 15 milliamps, The frequency determining components are all mounted directly on the rotary switch sections. The unit covers from 10Hz to 109.9kHz in four ranges. 48 SILICON CHIP as set by the "Vbe multiplier" QB. The whole amplifier is DC coupled throughout and has negative feedback set by the 5000 trim pot VRl in series with a 5600 resistor. The shunt part of the negative feedback network is provided by two 24V 40mA miniature incandescent lamps. High frequency compensation, to ensure that the amplifier is stable, is provided by the 22pF capacitor connected between base and collector of Q7. Some readers may wonder why we have used an output stage operating in class AB. Wouldn't class A give better distortion? As a matter of fact, it wouldn't. The reason is that the amplifier is an oscillator operating at a constant large output voltage swing of 28.28V peak to peak. At this large voltage, any small crossover distortion effects which may be present are vanishingly small. Well, that's about all we have space for this month. Next month, we'll complete the circuit description of our new oscillator and conclude with the full construction and setting up procedure. !b< WALL CLOCK WITH T & 'SPY IN THE SKY' SENSOR RETURNS DITY The Pyroelectric infra-red sensor element in this 'eye' of a passive infra-red detector. Typical applications - burglar alarms, proximity detectors. auto door/shutter switch. toys/robotics etc. Spees: ■ Wavelength range 6.5 - 14 um ■ Peak signal (typ)<at> 250W/cm2 incident energy BOOuV ■ Frequency range0.1 Hz - 20Hz ■ Operating voltage 3 - 10V Cat. ZR-9500 A precision quartz movement clock which incorporates both temJErature and humidity. Includes AA Alkaline battery. Cat XC-0120 $29.95 Simple PC-Driven Funtion Generators Kit Ref: EA January 1989 This is a sijmple and low cost kit which lets you use your personal computer to generate signals with almost any conceivable waveform. See catalogue for details Radio Teletype Modulator Kit $19.95 Ref: AEM May 1987 Ideal companion to the very popular "Listening Post" kit. This simple, versatile unit is intended for attachment to a personal computer using software to generate the raio teletype (RTTY) Baudot code characters. For further details see our catalogue. Cat. KA-1709 Was $49.95 NOW $29.95 Cat. KM-3016 WAS $32.50 NOW $19.95 :SAVE ~ 12.55 NOW $40 Was $55 ARLEC TRANSRM R BARGAI ARLEC No. 61365 A chassis type tranny that gives 240V to 24V CT <at> SOOmA and 9V <at>SA/ This tranny could give you a ±12V 500mA and +SV<at> 5A DC power supply (with rectifiers. regs, and electros of course). Caal. MA-2600 Normally $25 ~t£~Y~n P&P$4extra ~ I ul · ~ ARLEC No. 61435 Agrain oriented steel chassis type unit giving 240V to 'iN AC <at> 3A. 16V AC <at> 2A. 16V AC<at> 1A. The secondaries can be wired to give 16V<at> 3A or 24V <at> 3A. This is ideal for burglar alarm power supply as burglar alarms use 16V. You could also make a 13.BV regulated power supply from this. ~ Normally $30 - $35 \ -----=: ONLY $9.95 10+ $8.95 Cat. MA-2602 P & P$4 extra ll" .· ~ ARLEC No. 61439 An in-line "Maxi box· type power supply. 240V to 6V AC <at> 3 AMP. (Output lead fitted with 5.5 OD 22.110 DC plug.) Normally worth $40 --~,..___ ONLY $9.95 --..:.10+ $8.95 Cat. MA-2608 SAVE $15 DIGITAL CAPACITANCE METER NEW Anew addition to or range of test equipment. (deal for checking tolerances, measuring unmark ed/unreadable values, sorting values, selecting matched sets, measuring cable, etc. 31/2 digit LCD display over 9 ranges. Includes zaro adjustment knob. Overload fuse protected. Three months guarantee. Cat. QM-1572 ·uo· Satellite Decoder Kit Ref: AEM October 1987 The University of Surrey (UK) maintains two satellites - Uo-9 and Uo-11 . Information transmitted is of an educational. amateur radio or technical nature concerning the satellites themselves. See cat for further details Cat. KM-3003 Was$55.00 NOW $29.95 .,S VE $25.05 Ref: Silicon Chip Jan 1989 A line filter kit for your computer which incorporates an effective filter for mains borne interference and a varistor to clip dangerous spike voltages. Kit is mounted on a metal box (differrent to one shown in photo) and has 4 mains output sockets with a total load of 1kW maximum. Kit includes PCB, box (HB-5446), 4 mains sockets and all specified components. Cat. KC-5046 Ref: EA March 1989 This unusual project is actually a metronome that has its rhythm set by simply tapping the unit at the desired rate. The Jaycar kit includes case. speaker and all electronic components. It runs on a 9V battery (not supplied). Size: 130 x 68 x 41mm. Cat. KA-1714 Was $29.95 !DRILL MAD ESS This direct import product is outstanding value for money. It is moulded in a high impact dark grey plastic case with inbuilt tilting ball, includes spare fuse (built-in) and colour coded panel. A very comprehensive instruction manual is provided. CAPACITANCE RANGE 2nF • 20nF • 200nF • 2uF • 20uF • 200uF INDUCTANCE RANGE 2mH • 20nnH • 200mH • 2H • 20H See catalogue for full specs Cat. OM-1575 WAS $219 NOW $189 SAVE $30 Specifications: Range Resolution 200pF 2nF 20nF 200nF 2uF 20uF 200uF 2,000uF 20,000uF 0.1 pF lpF lOpF lnF lOuF lOOnF luF lDuF a·/ MINI DRILLS IN PKTS DF10 ■ ■ ■ 0.8mm x 10 (Cat. TD-2420) 1mm x 10 (Cat TD-2421) 1.2mmx lO(Cat. TD-2422) ANY PACK ONLY $9.9!i 0.8mm Cat. TD-2408 SAVE 704 1mm Cat. TD-2410 SAVE 90\l ■ 1.2mm Cat. TD-2412 SAVE 90\l ANY ONE ONLY DIGITAL CLAMP METER • Cat Price $139.95 NOW $99.95 DRILL PACK Includes all those commen ones: ■ 1 x 3.5mm - for PC supports. relays ■ 2 x 1.2mm - for PC pins. hook-up wire ■ 3 x 1mm - for resistors. capacitors etc ■ 4 x 0.8mm • IC's etc. TOTAL 10 DRILLS FOR ONLY $12.9!i . Cat. TD-2400 - WERE SELLING FOR $24 · ■ ■ INTRODUCTORY PR CEO LY 109. !~~ Are you sick of paying high prices for mini PCB drill bits? We were. Now you don't have to pay outrageous prices anymore. Jaycars direct imports save you money. LOWER PRICES ON SINGLE BUYS lOOpF c!~!/~~~ed and accurate at a low price - see our catalogue for full details Cat. DM-1570 10+ $18.50 Fresnel lens for movement sensing Cat. LA-5025 $3.95 10+ $3.50 £~ $1,50 $59.95 Another surplus buy, which saves you a fortun e. Hig h qua li ty Japanese made Nippon Chcmicon brand . 3,JOOuF 63V RB 3,JOOuF 80V RP 4,700uF 63V RP 6,800uF 40V RP 10,000uF JSV RP Normal Price $7 50 $8.50 $8.50 $8.50 $11.00 EX DE L BATT I 1.9AH $14.95 C size Was $11.25 ea NOW $6.50 EA Cat. SB-2459 SUNRISE BRAND 1.2 Ah D size Was $11.98 ea NOW $6.95 EA Sale Price 10+ S3.95 S4.95 S4.95 S4.95 S5.95 $3.50 ea Cat. $450 ea Cat. $4 50 ea Cat. $4.50 ea Cat. $5 50 ea Cat. RU -6730 RU-6731 RU-6732 RU-6734 RU-6735 ~i EL \ I 10+ $13.95 Cat SB-2482 2.6AH $19.95 10+ $18.95 Cat SB-2484 15AH $59 WAS $79 10+ $55 Cat. SB-2490 C & D NiCads SAVE UP TO 42% If' s AD Similar to QM-7200 but• 16 character alpha-numeric LCD display• Capac ity 8000 alpha -numerics • Superior editing of old informa tion • Soft rubber tac tile keypad • 14 digit calculator with memory • Character search • Forward search Only requires 4 x AM batteries. Measures 155 x 103 x 35. Very high performance unitl Cat. OM-7026 ELFC ROL RP/ I I G l - A MULTIMETER KIT Ref Si licon Chip Feb '89 a· woofer and dome tweeter with pre-built crossover Acclaimed for its superb sound . The cabinets measure 480(H ) x 300(W) x 290(D)mm See our 1989 catalogue for further information. Pair of speakers and crossovers Cat CS-2540 ~ee Silicon Chip Nov '89 Ideal for students. wh o can now build something really useful. Multi meter specs: 20,000 ohms/volt, 23 ranges. continui ty buzzer Si1e 135 X 90 X 40 $149 Ca t. KC-5058 Cabinets (pair) Cat. CS-2542 0 L $34.95 $129 SAVE$28 STEREO C ActoNUNT SPEAKER OPEN PIR DOORWAY/MINI ALARM Manufacturers! Open an account This pocket size alarm has a buil t in PIA sensor to detect human movement. It is ideal as a personal alarm or a shop door monitor. It wi ll either give a pleasant chime to announce cu stomers. or an alarm sound. It's e~sy to install and measures only 108mm x 67mm x 35mm. It oi:crates on a 9 volt battery. Cat. lA-501 2 with Jaycar ! Find out more by calling in to any Javcar store or call 1021 747 2022 or send us a Fax 1021 744 0767 • or write ! We will send you an accou nt application form by return. It' s that simple! ONLY $49.95 ~;; ll L G tool s. Ca t. AS -3050 REMEMBER · JA YCAR WILL NOT • tl • iLI 111 -.-:-1 SYDNEY - CITY P RRAMATTA NCORO VISA RSlVILLE lftlfl This is a complete system ready to insta ll in your home. It consists of: 2 x 4' dual cone quality spea kers• 2 x Spea ker grills and sc rews • 1 x SOW stereo volume controller• 2 x 20m rolls speaker wire. Ideal for games room, bedroom. ki tchen. den. etc. Simply connect to your Hi -Fi system auxiliary spea ker outlet. Full connec ti on diagram supplied. Eas ily installed with simple hand QA HEAD OFFICE 115Pa",~"° 2137 Telephone ROOO (02) Coom,d 747 2022 Telex 72293 FACSIMILE (021 744 0767 E MAIL ORDERS P O Box 185 Concord 2137 HOnlNE 02 747 1888 FOR ORDERS ONLY (008) 022 888 ROAD FREIGHT AN AYOU 117 York St. (02) 267 1614 • Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 3.55 Church St (Cnr Victoria Rd) (02) 683 3377 Mon-Fri 9 - 5 30 Thur.s A 30 rm - Sat 9 - 4pm 1 15 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.3J - Sat 8.30 - 12 121 Forest Rd (02) 570 7000 · Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 12 BURANDA QLD MELBOURNE-CITY SPRINGVALE VIC POST & PACKINCJ $10 - $24.99 $25 - $49.99 $50-$99.99 OVER $100 $ 3.75 $ 4.50 $ 6.50 $8 00 Alll 188 Pacific Hwy (Cnr Bellevue Ave)(02) 439 4799. MDfl-Fri 9 - 5.30 Sat 9 • 4pm 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 12 Sh(ll 2, 45 A.Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat9 - 12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 • 2 Not really but. this f,antastic little hand held unit covers most bands from 60-950 MHz! The unit works normal 25kHz spacing and also the mm 12.SkHz offsets. You can also programme up to 20 selected channels in this unit. You can also programme the unit to "search" a band of frequencies . When the scanner finds a transmission. it locks to it and displays that exact frequency on its clean LCD display The "Road Runner AR-ffiO measures 190mm high x 50mm wide x 45mm deep. It has a sturdy stainless steel belt clip and BNC connected ruber duckie antenna 150mm long . It is powered by 4 x AM batteries . If ever you thought of buying a scanner, this is the one I I 1. 2. 3 4 5 6 7. Children are encouraged to learn to compose music. spell, learn maths and play stra tegic games all on their own without supervision 11 8 f 9 Value at $149 Ca t. XC-3050 Cat. DS-6000 SPECIFICATIONS: Frequency Coverage 60 • 90 MH z 138 -174 MHz 406 · 525 MHz 800-950 MHz 0.4mv Lo. Hi. VHF Sensitivity at 12dB SINAD O.Smv UHF 1mv 830 • 950MHz Channels 20 Scan Speed Channels Per Second - 13 Search Increments: 5. 10, 125kHz.Lo,Hi,VHF, 12.5kHz UHF 25kHz 830 • 950MHz Power Requirements 6V DC <at> 60mA (squelched) Antenna Connector: BNC Display Type LCD ~ -E_ _ E * I QUALITY WIRE CU ERS ONLY $399 SAVE $1 0 41256 LOWER PRICE Duality "O.K." Brand, made in USA Were selling for $12 in 198511 Flush cutting, green cushion grips, 130mm long, cuts up to 16AWG. keeps clipped leads from flying. Cat. TH-1895 Memory Tune Math Ou11 Mu ltipl1 cat1on 0 Am I Correct - math prac tice Gegins With - firs t spelling Spelling Guess That Letter Automa tic or program manually Guess That Word Automa tic or program manu ally Letter Finder Number Finder 256K RAM 120n sec. ■ Qual ity Electrophon e Bra nd ■ Two way intercom pag ing fac ili ty ■ Recharge socket on handset ■ Pulse/Tone dia lling ■ 12 months warranty ■ Superb sound. a quality product Cat YT-7068 NOW ONLY $12.95 10+ $12.50 Cat. U-8435 ONLY $9.95 TI"L COOKBOOK Don Lancaster• 335 pages. A complete guide to the understanding and use of Transistor l ogic (TTL) integrated circuits• the basics of TTL are given. what it is. how to power it and so on . Also conta ins a catalogue of TTL devices. giving physical and electrical specs. $19.95 Cat. BS -0520 Oz-made unit that detects the noise made when glass breaks. NOT A SIM PLE ELECTROMECHANICAL DEVISE The unit consis ts of a plas tic case which conta ins an electret mic element coupled to an electron ic fi lter/amp circuit Adj us table sensitivity. When glass breaks the output connection goes log ic 'low · Easi ly connec ted to most car or house alarms Cat LA-5065 NORMALLY ABOUT $50 LIMITED QUANTITY IDEAL FOR CAR ALARM S ~ WAS $19.95 NOW $9.95 0 GAIN • * PAY ONLY $599 JANUARY ONLY " ~ o $ilJtl)ol~lmlllfO-~Dm'~~ ,_ , , : = ., • - -.,._ ' v~ ,~ .. ,. ,,..« ;;.':'v~-..::,~;'b"':~,. .i.,:'..c#;>t ·ft t"" ''\f/"!.:"tt~r.;:~}\:7:;.j'"'{ ,.:/[]Mi ; • , -~-- e' "" , < ,i. Designed for easy wire stri pping The Alloy steel 1aws ca n stri p all types of wire lrom AW G 10 • 26 gauge (0 13 • 6 Ornm) Incorporates a prec1 s1 on cutting blade for easy wi re cutti ng Also incorporates qual ity crimping 1aws· - for insulated terminals (1 5 - 6mm) - for non insulated termi na ls (1 5 - 6mm) · for auto ign1t1on termin als (7 - 8mm; This 1s the best all round wire 1001 we've seen for a long time Cat TH- 1826 $17.95 Purchase a Blueprint 60W RMS /channel stereo amp kit together with the new ste reo 1/2 octave equaliser and SAVE $119 Playmaster 60/60 Amp Cat KA-1652 $369 Stereo 1/2 Octave Equaliser Cat KC-5055 $349 $718 EAVY Y WIRE TRIPPER/ ~ FET VOM MULTIMETER Lots of features including 12 AMP DC and AC, high input imp. polarity reverse sw, safety test leads. See catalogue for full specs. Cat. QM-1050 Was $89.95 TIME Pre-programmed with 12 times• for different cities including Tokyo. Hong Kong, Bangkok, Sydney, London. Paris. Cairo. Moscow, Honolulu. Los Angeles, Chicago, New York and one spare zone for another city. The times are displayed immediately after touching the button. Also incorporated is a calculator as well as the date and an alarm. Credit card size. •once one time zone is programmed in. the other zones are automatically calculated by the unit. Cat. OM-7210 ST EQ IPMENT SAL WasS19.95 0 NOW 69.95 Audio Balanced Line Driver Kit Ref: AEM July 1987 This kit is a dual channel (stereo) unbalanced input to balanced line output driver. Ideal for driving an active loudspeaker system where the power amp(s) are in with the speakers. Kit includes: DIN. RCA & Cannon Sockets, box. PCB. and all parts including the expensive LH0002CH's. Cat. KM-3060 Was $99.50 NOW $59 SAVE $40.50 DELUXE BLACK RACK CABINETS WITH HANDLES - SAVE 0 Removable top and bottom panels. black finish with high quality brushed anodised front panel. Handles and rubber feet supplied along with all screws. nuts, etc. to assemble. SAVE 15% WAS NOW 5+ HB-5380 $39.50 $33.57 $31.00 $42.07 HB-5381 $49.50 $39.00 HB-5382 $49.50 $42.07 $39.00 HB-5383 $65.00 $55.25 $52.00 HB-5384 $75.00 $63.75 $59.50 SPEAKERS see cat for full technical specs ■ Minstrel 1N Dome Tweeter As used in the Minstrel 2/30 speaker kit, ref: Silicon Chip February 1989. This tweeter offers excellent top end quality at a very reasonable price for a dome tweeter. Was $19.95 .--.-:~;::;;:~ NOW15.95 SAVE ■ 8" Minstrel Woofer • ■ 8" Twincone 4 Ohm P.A. Ideal for multispeaker sound reinforcement where 4 ohm speakers are required. Quality speaker made in New Zealand. 10 watt power handling Cat. CE-2322 s Was$26.95 NOW $21.95 SAE ■ 6" Twincone Widerange This speaker has high efficiency and is ideal for extension speaker and low level sound reinforcement use. Cat. CE-2325 Good quality 6' dual cone speaker for replacements in small boxes. Cat. CE-2320 s Was $13.95 NOW$9.95 10+ $9.50 . Was$13.95 NOW$9.95 10+ $9.50 A.JE Fidel - y Ref: AEM October - December 1985 The definitive Preamplifier by David Tilbrook. The AEM6010 design is on a purist philosophy being that the less you put in the signal path the less likely you are to distort it. The aim of the project was lo design a unit that would challenge the finest commercial designs. Power supply requirements. Unit needs 30-35volts. i.e. +30V/0/-30V. If used with the 5000 power amp. the secondary power outputs in the 5000 are wired in series and will comfortably supply the preamp. If used on its own a toroidal transformer 30ft)/30 is recommended. See ca t for full specs. Cat. KM-3030 NOW $279 SAY $80 V Yet another fabulous scoop purchase. A compact high quality tuner that operates from 526 - 814MHz (corresponding to channels 28 thru 63). This tuner is designed for Australian standard reception (AS 10531973). and is offered at a very low price. Price includes circuit diagrams and connection drawing. This is a very cheap _way to convert a VHF only TV to UHF. (Some skilf may be required.) SPECIFICATIONS - see catalogue cat. DM-1000 Was $29.95 Was $14.95 NOW$9.95 Was$9.95 NOW$5.95 10+ $5.50 Ref: Silicon Chip February 1939 As used in our Minstrel 2/30 speaker kit. It incorporates a non press paper cone with butyl edge. Cat. CW-2113 Was $359 lJ Sanyo Model T1087RA Super Timer Kit Ref: EA Docember 1988 This kit is a low cost. but very . _____ ._ .. -- flexible. 4-digit timer. f:, Kit includes PCB. and ( \ ~ - ,,0 , _. ' '" all specified components./ \ Cat. KA-171l! \I \ Was$59 NOW $45 \ \ \ S " BULKHEAD MOUNT PLASTIC CASE A unique clip together case that features moulded in mounting feet on the sides. Measures 87(L) x 67{W) x 31(D)mm: Ideal for car burglar alarms, etc. Black in colour. CAT NO DESCRIPTION WAS NOW PP0802 9D IDC Male 9D IDC Female 9D A/Angle Male 9D A/Angle Female 15D IDC Male 25D IDC Male 25D IDC Female 370 Male 37D Female 37D Backshell Centronics Plug Centronics IDC Plug Centronics Socket Centronics IDC Set 16 Way IDC Header 26 Way IDC Header 34 Way IDC Header 50 Way IDC Header 16 Way A/Angle Hdr 26 Way A/Angle Hdr 34 Way A/Angle Hdr 50 Way R/ Angle Hdr 16 IDC Cable Socket 20 IDC Cable Socket 26 IDC Cable Socket 34 IDC Cable Socket 50 IOC Cable Socket 7.50 7.50 3.45 3.95 7.50 7.50 7.50 7.95 10.95 4.95 7.50 8.50 9.95 8.95 4.25 5.50 5.50 6.95 4.25 4.95 6.25 10.95 4.75 4.95 5.25 5.75 7.50 4.95 4.95 2.95 2.95 5.95 5.95 5.95 3.95 3.95 2.95 3.95 5.95 4.95 6.95 2.95 3.95 3.95 4.95 2.95 3.95 4.95 5.95 2.95 2.95 2.95 3.50 3.95 ~ PS0005 Normally $2.00 PPOBlO JANUARY $1.50 f./ ~~~ Cat. HB-6075 ~= ~ 10+ $1.25 SAVE .so~ PP0842 2~r: _ AVE 15% ON FIBREGLASS B RD ■ 150mm x 75mm Cat. HP-9514 Was $1.95 NOW $1.65 ■ 150mm x 150mm Cat. HP-9512 Was $3.75 NOW $3.18 ■ 300mm x 300mm Cat HP-9510 Was $9.95 NOW $8.45 DOUBLE SIDED ■ 150mm x 150mm Cat. HP-9519 Was $4.95 NOW $4.20 ■ 300mm x 300mm (approx size) Cat. HP-9520 Was $14.95 NOW $12.70 CENTRA CA C NG Install them over the holidays. See catalogue for full specs. ■ Master Door Lock Actuator PP0890 Another surplus buy. Utilux now only supply these connectors in black but they had a quantity of chrome plated ones and Jaycar bought the lot. There are two connectors, one line and one panel type. The line connectors are hermaphroditic. w~ich means they can be plugged into themselves for the line connection. Rts our jumbo speaker cable perfectly. You would normally pay about $10 each for these. Spees: ■ Mechanical: cable clamp withstands a cable pull out force of 30 Newtons. ■ Material contacts: copper iron alloy silver plated. ■ Body Shell: zinc alloy die casting chrome plated. ■ Electrical: Rated at 30 Amps continuious at 1OOV maximum. LINE CONNECTOR • 1 They've never been so cheap. 240V mains to 12.6V C/T<at> 150mA. Quality Ferguson brand. ~\ ~ - ~., ~ ' Was $99 0 100+ $3.20 including tax Save Door Lock Actuator 50W RMS MOSFET AMP MODULE J-50 SOW RMS min into 8 ohm with 25-0-25 2A transformer 1 x 4.700 uF/BOV filter cap each side and 3A bridge rect Ali' other specs the same or better than above. (Filter capacitor values must be doubled for use on 4 ohm leads.) Both units measure 136 x 128 x 74{H)mm including heatsink. Cat. AA-0380 J: JANUARY PRICE $3.95 ea NOW$35.05 PANEL CONNECTOR $2.95 Cat. PP-1082 () Normally $5.95 ea Was$38.95 $2.95 10+ $2.50 Cat. PP-1080 G) 2851 TRANSFORMER . - -... • - Cat. LR-8832 Suitable for front doors. ■ PS0864 PM0868 PP0892 PS0895 PS0896 PP0945 PP0947 PP0948 PP0950 PP0965 PP0967 PP0968 PP0970 PS0985 PS0986 PS0987 PS0988 PS099'.l SINGLE SIDED UTILUX UX HIGH PO ER AUDIO CON ECTORS LOWER EVERYDAY PRICES ON COMPUTER CONNECTORS 1/2P NOW$4 Cat. LR-8833 Use on back seat doors Was$36.95 NOW$33.25 ■ ■ Designed and manufactured in Australia. Ideal for improving picture quality when dubbing. See catalogue for full details. . . Heavy Duty Actuator Cat. LR-8834 Use on boot, rear doors. $79.95 Cat. AV-6501 Requires 12V AC plugpack Cat MP-3020 $16.95 Was$46.95 NOW$42.25 ■ Relay Used to operate the above. Cat LR-8835 Combined fader for high + mid speakers in a speaker box, or ideal as replacement pots if yours has blown. Handles 1SW or about 80 watts system power. Vertical style Purchase together this , :as:s;~_95 ' J;~ month for only $84.95 Save $11.95 7 A.. 20°,0 81-FET Preamp SMALL Super Hi Fi ~ 0.005% DISTORTION This magnificent preamp has many features: Phono in. phono out. auxiliary input, 'loudness· control, provision for a 'tbne defeat' switch, bass, treble AND midrange controls, a 40 detent click type volume control. (Requires ±15V 200mA power supply.) Size: 203 x 106 x 40(H)mm Cat AA-0315 Was $84.95 NOW $59.95 SAVE $25 NEW CATALOGUE? YUP, IN MARCH! MIDRANGE+ TWEETER LEVEL CONTROL BARGAIN Normally $9.95 JANUARY NI CCL ONLY $2.95 Cat. AC-1684 These have a syringe action and are ideal for working with small components. AED Cat. HM-3040 ~ BLACK Cat. HM-3041 s-;;;.i;;:l7S=-.1-1.i• Normally $1.20 . NOW .96c EA 1O+ .85e LARGE 137mm IC clip RED cat HM-3045 137mm IC clip BLACK Cat. HM-3047 ~/A r~~- MEDIUM 00mm IC clip RED Cat. HM-3044 OOmmlCclipBLACK Cat. HM-3045 A complete preamp and high power amp - with power supply electronics and loudspeaker protector in the one package. All that you need to connect is a power trar,sformer and a signal source. See catalogue for full details. Transformer to suit Cat. MM-2015 $69.50. Normally $1.50 Was $169.95 NOW $1.20 10+ $1.05 SAVE $40 ONLY $129.95 ~ Limited Oty , Normally $2.95 ·· . - , NOW $2.36 10+ $2.15 ·. 10% OFF A L TV ANTENNAS & ACCESSORIES FOR A UARY PRO SERIES POWER AMP KIT 00000• • FNHF INDOOR TV PllflER SPLITTERS LT-3819 REF EADec'89.Jan'90 This unit has a 75/300ohm input and two 75/300 ohm outputs. Further splitters can then be used as this unit is designed to drive up to 8 - 10 TV points . It also has a channel 3, 4, SA and FM switchable trap (-25dB) in case of cross modulation of lBdB x 2. :: S~:: amp design has been totally redesigned t o accommodate latest technology I This totally new design features the best of the old ETI 5000 features including: ■ Magnificent heatsink front panel ■ Rugged chassis bar 2 rack unit construction ■ Proven Hitachi Mosfet technology ~n~~st~e~~!a~o~ Was $109 BUT ALL ELSE IS NEW! The new pro Series I features two especially European made 22SVA Toroidal Transformers feeding two separate power supplies. one for each channel. (The ETI 5000 had a common power supply for both channels). This massive bank of energy not only increases channel separation. but gives the amp an ENORMOUS LEAP in POWER HANDLING. (See specs.) Better Features. The Pro Series I not only kills the 5000 for perfomace. it has great features. For example. it has a chassis plug IEC 320 style mains inlet and a switched chassis IEC 240\/ socket to power other mains equipment. It also features signal clipping LED's on the cast front panel. This keeps in mind the highly likely professional applications for this amp. Simpler to Build. You would think that this new amp would be harder to build than the straight forward 5000. Not sol The Pro Series I. infact. is far easier to build and actually has less signal distorting components than the 5000. What do you pay for this magic? Incredibly. we have managed to well withing sight of the old 5000 - only $100 more. That's right I You get all this for only $59911 INCREDIBLE. NOW $69.95 I EWLEDP Bargain of the century \ 100 assorted LED's including 3mm and 5mm in yellow, orange, red a,nd green. rectangular, triangular and other shapes and displays I Al I for less than 9t each I ~ ::::';: Ja,a, kli ' " - \ \\ ., ,' \ $8.95 Cat. ZD-1696 j •-\' · wi$ '"99~"·,olhioo I Oa lo S. · a,a 'l ~ Specifications Playmaster Pro Series I ( f ~ Power output (per channel, with both channels driven) Continuous 140W RMS into 8 ohms 200W RMS into 4 ohms IHF pulse power: 190W RMS into 8 ohms 320W RMS into 4 ohms 0.005% at 100W RMS into 8 ohms Harmonic distortion 0.007% at 140W RMS into 8 ohms 0.008% at 200W RMS into 4 ohms Intermodulation distortion 0.004% at 100W RMS into 8 ohms (41 ratio of SCHz and 7kHz) 10Hz to lOOkHz (-3d8 points) Frequency response More than 1OOdB below rated output (unweighted) Signal to Noise 0.83V RMS for 100W into 8 ohms Sensitivity Approx 33k ohms Input impedance Output slew rate More than 60V/us Damping factor Greater than 50 Activated if output distortion exceeds 0.05% Overload indicator ITS KA-1717 Subwoofer Adaptor KA-1718 Auto NiCad charger KA-1719 NiCad discharger KA-1720 RGBI to PAL encoder KA-1722 Low cost mains filter KC-5050 1/3 Graphic equaliser KC-5051 CD compressor KC-5052 Touch lamp dimmer KC-5053 Extension touch dimmer KC-5054 Garbage bin reminder KC-5055 1/2 sterep graphic eq. KC-5056 FM radio/motorbike intercom k, J""' """"hi as a:~fi s $29.95 $42.50 $27 .95 $39.95 $18.95 $239.00 $49.50 $32.95 $14 .95 $24.95 $349.00 $69.95 .UALITY DISKS AT SILLY PRICES 5 1//4' DSDD 48TPI fit,c;; iicrr- ,. . . .. Cat. XC-4730 $6.50 for 10 3 l/2° MF2DD 135TPI Cat. XC-4736 ◄ $26.95 for 10 5 1/4' OSHO 96TPI Cat. XC-4732 $18.95 for 10 Lifetime warranty Scoop Purchase! 12 KEY NUMERIC PAD (telephone le) This fantastic little keypad measures 67H x 44W x 7D . Each button is separately addressable a;id has a fantastic tactile feel . 0-9 plus• & I keys. Connection data provided Japanese made. Quality . $2.50 each OR 5 for $10 L ~ Cat. Al-5510 $69.95 Includes two headsel/mics and amplifier. Cat SK-0760 HHIUU'P ·- NTE CO Ideal for ul tralight aircraft, power boats. etc. Slim earpads stick to the inside of the helmet wi th velcro. Mic does the same. Safety line plugs uncouple in emergency. Amplifier unit fits into any jacket pocket. Battery powered. SURPLUS 0 CASH Jaycar will purchase your surplus stocks of components and equipment. CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 747 2022 IN4003 DIODES 1 Amp 300 vol ls Save$$$$$ 50 for $3 100 for $5 STOCK UP NOW Cat ZR-1003 I POV' [ Convert your normal hand operated window winders to power windows. It's really simple to connect. remove the manual handle. choose the correct adaptor and connect to motor drive and mount the drive unit. Supplied with cables and auxiliary switch . Cat. LR-8810 POWER WINDOWS FOR ONLY $219 WELCOME 1990 A BURGLARIES ARE UP AGAIN . ... Install your burglar alarm In January and save! Not only money, but all your belongings! ARE YOU PROTECTED? "' LARM PANELS Key operated Cat. LA-5162 Was $149 Save $20 $129 e Keyless model Cat. LA-5168 Was $229 S ve $30 $199 Keyless 4 Sector . 75 rA,------- $249~ ~ ~$$~ PIR D TEC ORS Our best selling model Cat. LA-5017 Normally $69.95 Save O ONLY $59.95 Teminator Pulse Count Now with 5 year warranty Was $99 Now $89 Cat. lA-5018 TheBestPIR Cat. LA-5019 Sa e $10 Was$139 Save $10 ►► PURCHASE ONE ALARM PANEL and TWO PIR'S in JANUARY and we'll give you 10% discount on all the, other alarm accessories you need to get the system running - e.g. horn speakers, covers, cable, reeds/ magnets. Now $129 DIGITAL ACCESS YPAD Cat. LA-5160 Was $109.50 Less 10% $98.55 EXT Metal. including tamJEr switch Cat. LA-5110 Was $23.50 Less 10% $21.15 N COVER RE ET N.O. and N.C. on the ooe assembly Cat. LA-5070 32 metres Iong Was $4.7 Less 10 $4.27 ./:7>~'"""-,. Was $12.95 , Less 10% ff!!I~ $11.65 i· . Cat. LA-5050 LARGE SCREECHER SIREN Unbelievable ear splitting sound. 120dB of it. Operates on 12V and draws 300mA. Ideal for burglar alarms where deafening sound is required and space is not a problem. Size: 110(W) x BS{L) x 100(H)mm. Cat. LA-5720 • t f:" WAS $24.95 JANUARY $14.95 SAVE $10 " ..... rA \ ,c· Made in Italy - grey in colour. 12 volt with unbearable sound. Size: 57(L) x 33(H)mm Cat. LA-5254 WAS $17.95 NOW $9.95 The Sensational 30 Piece Engineers Driver Set G /TAR SPEAKERS 1 15" 150W RMS At last! A driver set incorporating those obscure shaped heads! This set contains all the driver bits you are EVER likely to encounter. ■ 5 slotted bits 0-1, 3-4, 5-6, 8-10, 12 ■ 5 Hex bits 3/32", 5/64", 7/64", 1/8", 8/64" ■ 4 Phillips bits No. 0, 1, 2 & 3 ■ 4 Square Recess bits No. 0, 1, 2 & 3 ■ 6 Torx bits Tl0, T15, T20, T25, T30, T40 ■ 2 Pozidrive Bits No. 1 & 2 ■ 1 x 1/4" Drive Socket Adaptor ■ 1 x 1/4" Drive Hex Bit Holder And it's all housed in a sealable tough plastic case. Cat TD-2000 Cat. CG-2382 $129 12" 100W RMS Cat. CG-2380 $89.50 10"65WRMS Cat. CG-2379 $59.50 STILL ONLY $19.95 Brand new MOTOROLA POWERLINE horn. Includes a protection circuit internally which allows the new horn to handle 400W RMS. It uses a miniature light bulb and a PTC resistor. Under extreme high power surges.,the PTC opens up allowing the speaker to continue to play, at a somewhat compressed power level. The resulting product is a practically blow-out proof speaker. Replaces KSN1025A. M Size 177.8 x 82.55mm. Rectangular. Freq Response 1.9 - 40kHz. Volt Sensitivity <at>2.83V 1/2M- 100d8 Ideal for Hi-Fi and Sound Reinforcement Cat. CT-1912 SAVE 15% ON PHOTO ETCH E See our catalogue for dull details Description Cat. No. Film developer & Fixer NC-4264 PCB Etch Resistant NC-4266 Developer for Etch Resistant NC-4267 Co~ing Film 125x150x6 NC-4270 Co~ing Film 200x275x2 NC-4272 400 I i ONLY __.., $37.95 NORMAI.LY15% OFF $10.95 $9.31 $18.95 $16.10 $11.95 $10.16 $17.95 $16.25 $17.95 $16.25 ' lush Cutters • 110mm A more compact version of the TH-1891 cutter exept with Japanned (black metal) finish and leaf spring return. Vinyl handles. Was $ ~ ~ .. 9 . 5 JANUARY $6.95 . :SAVE $3 · Cat.TH-1892 ~ HEAVY, HEAVY DUTY FIG 8 Solder Reel ga 200 gram reel. 1mm universal guage. Suitable for all types of electronic soldering. Resin cored and including bit ~;,~,-, ::~w Was $7.25 NOW $6.25 ;SAV $1 If you want something better than our heavy duty speaker cable, and the Jumbo cable is too large and expensive. then this is what you need. It is 2 x 79ft).2mm. which is exactly 1/2 the wire content of the Jumbo cable but still 3 times thicker than the heavy duty cable. 2WayScrew Down Speaker Terminals ·cutters • 120mm White with black trace. ■------• Cat. WB-1712 Was $1.S0mt _:,__ _ __ Cat. PT-3008 Was $1.00 JANUARY $6.95 / Lf? SAVE $3 ~ -=----=,--- JANUARY $1.20mt ,SAVE 60~ NOW , .so~ EA 10+,40~ .RED ILLUMINATED 240V 0.4mm Single Core 1RO KER SWITCH BARG IN Hookup Wire ~ <. , , , ~~-, ,. 240V 8 AMP DPST Cat. SK-0985 _ -· ~i...-- ~ 11 Normally $3. 95 ~J ,_, ~ ij '-' JANUARY PRICE $1.95 SENSATION ... Telecom style 0.4mm single core insulated. 250m roll Cat. WH-3027 $4.95 500m roll Cat. WH-3028 $8.95 SAVE A FORTU E 10+$1.SO ~ JUMBO ~ SPEAKER CABLE For the audiophile who wants the best of speaker cable. Figure 8, 259 strands in each side. DC resistance 0.003 ohms per foot. Inductance 0.23uH per foot. You can hear the difference. Cat. WB-1732 j Was $3.50 mt JANUARY $2.50 mt SAVE $1 . . '• · - Wide bandwidth and high sensitivity- Internal graticule rectangular bright CAT - Built in component tester - Front panel trace rotater - TV video syno filter -Z axis (intensity modulation)- High sensitivity X-Y mode - Very low power consumption - Regulated power supply circuit Cat. OC-1900 Probes to suit Cat. OC-1902 $699 $49.50 ea . .1 Similar to TH-1890 except larger 11,1erall and with captive coil spring return. Vinyl handles. Cat. TH-1891 Was $9.95- -· BOOKSHELF Project book for CMOS ICs and more reliable. There is currently a lack of practical books that fill the space between very basic digital theory and the theories of LSI but this text does quite a resonable job of filling that gap. Our copy came from Dick Smith Electronics (Cat. B-1252) and is available for $29.95. (D.B.Y). Repairing CB radios 50 CMOS IC Projects, by Delton T. Horn. First edition 1988, published by Tab Books Inc, Blue Ridge Summit, PA, USA. Soft covers, 188 x 235mm, 210 pages. ISBN 0-83062995-5. Price $29.95. Many books on digital electronics delve right into the theory and don't give practical circuits a second thought. This book fills this gap by supplying 50 circuits of varying difficulty. It starts off with a chapter on the basics of digital electronics, then come nine other chapters covering binary and control circuits, test equipment, LED flashers, signal generators & music-making projects, counter and time-keeping circuits, games and other miscellaneous circuits. The projects include a digital capacitance meter, freque ncy dividers, multipliers and multi-digit counters. Although there is an assumption of elementary electronics knowledge on the part of the reader, each project is described in an easy manner with a background discussion to give the flavour of the project, without requiring mountains of theory. Each project is accompanied by a clear circuit diagram and a comprehensive parts list. There are also handy tips that make designing logic circuits easier The "Screwdriver Expert's" Guide. Do It Yourself CB Repairs and Modifications, by Lou Franklin. Published 1988 by CB City International, Phoenix, Arizona. Soft covers, 210 x 277mm, 96 pages. ISBN O 943132 39 8. Price $17.95. In the November 1988 issue of SILICON CHIP, we featured a comprehensive article entitled "Screws and Screwdrivers: What You Need To Know". It gave a lot of information not previously published on special types of screwdrivers and so when this book came in with the reference to "screwdriver expert" we thought "Bewdy! More good info on screwdrivers and such-like". Well, we wuz wrong. It has nothing to do with screwdrivers. Instead, the book is on CB repair and aims to give a general look at the more common problems that occur with CB radios. The book starts off by introducing the reader to the "tools of the trade" and then goes through various sections, looking at mike problems and wiring, antennas, and the concept of Standing Wave Ratios (SWR). The author then looks at antenna basics, including antenna matching and coax connectors. The next 20 pages are devoted to a problem/cure section which is of a general nature, for example, radio lights up but is dead on transmit and receive, except for weak hissing noise etc. Other sections include phasedlocked loop (PLL) radios, introduction to frequency conversion, igni- tion noise and television interference. There is a new appendix section in this edition that describes basic frequency conversion for PLL radios, and conversions using crystal-exchange methods, frequency modifications on ROM-controlled PLLs, and AM to FM conversions. There's also a six page section which gives brief details of how to adjust transmitter output power on many of the common CB radios. However, since this book was published in America, it probably won't apply to many models here in Australia. Still, it could be of use where the user does not have a circuit diagram of a particular model. The final two pages will be of use to those just starting out to fix faults in their gear. It's a diagnostic flowchart, be it a fairly general one, but is in the general flavour of the book. In summary, this book is a useful source of general knowledge without all the hard theory and maths that goes behind it. It's written in an easy communicative style with reasonable sketches and figures, without being overbearing on technical issues. For anyone interested in CB radios, it is good reading. Our copy of the book came from Dick Smith Electronics (Cat. B-2324). It sells for $17.95. (D.B.Y). THE "SCREWDRIVER EXPERT'S" GUIDE JANUARY 1990 57 Sing it again Sam(sung) My main story this month concerns a brand of set which is relatively new to the Australian market. So, as well as discussing specific technical problems, we will take the opportunity to present some general background to it. The brand involved is Samsung, a Korean based company represented in Australia by Samsung Australia Pty Ltd (10/16 South St, Rydalmere, NSW 2116). As I said, this is a relatively new brand on the Australian market, having come to local prominence only in the last 12 months or so. And quite naturally, customers are tempted to ask just what kind of an organisation is behind this brand name. Fair enough. Well, for starters, while the brand name is new, the products have been around for a good deal longer. Most servicemen will recognise them as having been previously marketed under the 58 SILICON CHIP "Princess" and "Palsonic" labels. They are a large organisation. As well as TV sets, they also manufacture video recorders, audio equipment (including CD players), microwave ovens and computers. Their products are well established in the United States and they have manufacturing interests in other countries as well. Indeed, the brand has been well known in New Zealand for several years, where Samsung has a small assembly plant. They also have a very large manufacturing plant in Wales producing TV sets, video recorders and microwave ovens for the British market. So Samsung is no pip-squeak, fly- by-night organisation; it is just that we have only recently become aware of it in Australia. Samsung service My association with the brand began when one of the local dealers, for whom I do warranty and other service work, decided to market these sets. As part of the deal, he was required to organise warranty service so he suggested that I might be interested. Well, I am always interested in more work. At a technical level, my experience with the Princess and Palsonic models over the years had indicated that they were fairly conventional sets. In fact, they were no more difficult to service than most other brands. More to the point was whether Samsung and I could reach a satisfactory agreement. As many of my colleagues will testify, warranty service has not always been the happiest arrangement in the past, at least with some companies. What has seemed like a reasonable proposition in theory has not necessarily proved so in practice. Anyway, the dealer passed my name on to Samsung and they in turn approached me. Alerted by some of my previous experience with warranty work, I laid it on the line that I would need certain firm undertakings before committing myself. First, I needed to be assured of the ready availabilty of properly prepared manuals. A lack of manuals, or manuals that are not well written, can be more than simply frustrating; it can be very expensive, particularly with new or unfamiliar models. As a result, what should have been a modest profit can become a substantial loss. The next question is technical backup. While it is unreasonable to expect a company technician to have an immediate answer for every "funny" that turns up in the field, there is nothing more frustrating than talking to someone who obviously knows less about a piece of equipment than you do. So could I bank on adequate help when I needed it? Finally, there is the question of spare parts. Of all the frustrations we face, lack of spare parts is one of the most serious. It is often a big enough problem to diagnose a tricky fault without then facing the situation that the vital part involved is "on back order". Such situations can mean a delay of weeks or even months, while the customer fumes and the servicem~n becomes the meat in the sandwich. And it doesn't help that some customers refuse to accept that this is the true situation, preferring to believe that it is the serviceman's own laziness or incompetence (which, I regret to say, is true in some cases) that is the cause of the problem. Anyway, those were the major points I raised. And the company didn't quibble; they were eager to assure me that all those conditions could be met and so far they have been as good as their word. I only hope that they can keep it that way. But it wasn't a one-way deal. They wanted some assurances and background from me. In particular, they wanted to know how long I had been in the industry and asked questions about my workshop facilities and test equipment. Since I've been in the game for more years than I care to think about, and since my shop is as well equipped as anyone's, I didn't have any problem meeting their requirements. And so an agreement was reached which means that I am now an authorised Samsung service centre. Basic models All this happened several months ago and since then I have had the opportunity to come to grips with these sets at a practical servicing level. The range includes 34, 40, 45 and 48cm models and all appear to be designed around a fairly basic chassis, with only minor variations. There is also a portable set, designed for both 240V AC and 1 ZV DC operation. It uses similar basic circuitry. The most recent addition is a 63cm model but I have no data on it yet. The basic chassis is the P/50F and the sets based on it, which I have encountered so far, are the CB515F and CB515Z, both 45cm models. The "F" version uses an 8-channel pushbutton tuner while the "Z" version is fitted with remote control. The "F" version is a very popular model and my dealer friend has sold a couple of hundred so far, many to local motels. Apparently, motel owners regard the "F" version as ideal - it's a simple set, the size is right, and the price is attractive. One motel alone recently purchased 29 of these sets. In fact, I've opened a special file on these. Since they all came on line at the same time and are operating in the same environment, they should provide a lot of valuable service data. The nitty gritty Y~'P, NOION~ COMPLAIN-,- ABO OUR -rv S Now let's get to the technical nitty gritty. What I am about to relate covers virtually the same fault in all cases, producing the same major symptom but with varying secondary symptoms if neglected. The major symptom is a bright vertical line in the centre of the screen. This is an unusual symptom in that it obviously indicates a deflection failure but no accompanying EHT failure. An extreme side effect of this symptom, if it is allowed to continue, is a burnt board. This happened to a motel set on one occasion and left a hole big enough to pass a 5c piece. Digressing for a moment, this raises another matter which is peculiar to the motel scene. Faults in motel TV sets can often go unJANUARY 1990 59 SERVICEMAN'S LOG -CTD noticed for days, or even weeks. Most guests stay only one night and, unless they are TV addicts or wish to catch a particular program, a faulty set tends to be shrugged off as bad luck. By the morning it is forgotten and no-one is any the wiser. A further complication arises when the fault is intermittent, as it often is in this case. It may escape routine inspection or, worse still, may be deliberately left in service on the basis that it works for most of the time anyway, so why worry. I am now trying to instill some sense of responsibility into those concerned by emphasising the need to take a set out of service immediately this fault - or any fault - is observed, to avoid the risk of further damage. As already stated, the problem involves the horizontal deflection circuit, as distinct from the horizontal output stage. More precisely, it involves the area around inductor 1401 which is in series with 1408/ C414, side pin-cushion coil T402 and the horizontal deflection coils (see Fig.1). The problem is basically one of quality control, because it boils down to a series of faulty soldered joints. And note that I said "faulty" rather than "dry", because my im. pression is one of fractured joints, such as occurs when the two components are allowed to move before the solder has properly set. It is not an unusual fault and some early local production runs produced boards which were literally riddled with such faults. They were so well known that we treated them as routine. To be fair to Samsung, they are aware of the problem and have taken steps to correct it. In the meantime, those sets already in the field have to be dealt with. And again, to their credit, they didn't hesitate over the burnt board. I returned the set to them and they simply replaced it with a new set. The main offender is the joint at the" hot" end of 1401. If allowed to persist, this will destroy R413 because all the horizontal current 60 SILICON CHIP HORIZONTAL DEFLECTION _ ___._TO COLLECTOR OF 0404 R430 150{) C454 1 R~i3 L401 .,. TO HORIZONTAL OUTPUT TRANSFORMER Fig.1: this simplified diagram shows where the bad solder joints can occur in the Samsung CB515F. The immediate symptom is intermittent loss of horizontal deflection but damage to the board and to components can also occur if the sets are left in service. involved must now flow through it. Another version of the fault involves C414, which may be faulty at either end. In either case, prolonged use of the set in the fault condition can result in a burnt board in this area. Other secondary effects encountered so far include destruction of the horizontal output transistor (Q404), R423 or R420 (both rn ½ W safety resistors), and diode DHl or its associated resistor, RHl. The important point to note here is that the set may be presented to the serviceman as completely dead, due to one of the abovementioned secondary failures, and may appear to be fixed when the faulty component is replaced. In fact, the real cause - the faulty joints may simply be lying dormant, ready to strike again. So be warned. From southern shores Talking about vertical lines on the screen, here 's something from our southern sub-continent, as told by J.L. I thought I had seen just about every kind of TV fault there is but one showed up recently that really had me guessing. The set was a Sharp CX4846 and the "funny fault" was not immediately apparent. It came in with a report that the screen was very bright, with retrace lines, and that it sometimes switched itself off. No mention was made of the fact that there was no picture but that was the case. The excessive brightness was not all that difficult to solve. Somebody had been inside the set and had turned the screen (G2) control to full on. The excessive beam current under these conditions was close to the shut-down level for the power supply, which explained the occasional switching off. The final evidence of unqualified intrusion was that six of the 10 screws securing the cabinet back were missing and the remaining four were all loose by several turns. Mr Nobody It's funny, though. Quizzing the owner produced the answer "Oh, no! Nobody's touched the set". That Mr Nobody has a lot to answer for. Turning the screen control down to about half way produced a typical snowy screen and the retrace lines disappeared. It was at this point that the "funny" appeared. Right down the full height of the screen, about one third of the way from the left-hand side, there was a dense black band a bout 35mm wide. There was no sign of a picture, with each of the 10 channel buttons producing identical snowy screens. It transpired that Mr Nobody had not only fiddled the G2 control but also the channel selectors. My next job was to retune the various channels. The self-search tuning in this set was very slow and it seemed to take forever to get the first channel on screen. When I did, I could see the fault in all its final confusing glory. The black band had grown into a 75mm wide strip that had every sign of being the horizontal blanking bar. I had seen this in other sets when I had floated the horizontal scan but I had never seen it rock steady in an otherwise perfect picture. ("Floating" involves disconnecting the horizontal sync pulse and then adjusting the hold control until the picture "floats"; ie, almost stationary or drifting slowly from side to side. The trick is a useful one to This photograph shows the displaced image on the faulty Sharp CX4846. The black vertical band is the horizontal blanking period and the image at the extreme left belongs at the extreme right. determine if horizontal instability is caused by a bad horizontal oscillator or by faulty sync pulses). A Philips PM5544 test pattern from SBS showed just the extreme right hand side of the test pattern, on the left hand edge of the screen. After the right hand castellations, there was a narrow band of grey down the picture, then the solid black bar began. Right down the middle of the bar was a narrow green line, then more black bar before another grey strip, then the left hand castellations at about a third of the way across the screen. The rest of the test pattern was free of horizontal or vertical non-linearity although about a third of the circle was lost. As a matter of interest, the green line was the chroma burst. The sync pulses were buried in the first half of the black band and, because they are "blacker than black", could not be seen on this picture. Fixing it So that was the nature of the fault and it was now up to me to find out what it was and fix it. I mentioned earlier that someone had turned up the G2 control. My first thought was that they had also meddled with one of the horizontal presets and so messed up the horizontal timing. But there were only two horizontal presets, a horizontal frequency and a horizontal shift, and neither of these had been touched. Nor would any adjustment correct the fault. This seemed to be a case of "false line lock", a condition that I have heard of but never seen. It occurs when something either delays or advances the triggering of the horizontal oscillator. If the trigger was 32 microseconds late (or early), the blanking bar would be near the centre of the screen. In this case the triggering was probably about 42µs late (or about 22µs early). Horizontal oscillators are invariably of the "flywheel" kind, designed to prevent noise accompanying individual sync pulses from causing random triggering and "shimmering" in the horizontal plane. These oscillators usually have an LC circuit that can be adjusted to run at approximately the horizontal line frequency. This is then phase locked by a discriminator circuit that compares the timing of the sync pulse with a pulse from the flyback transformer. The whole system is given a relatively long time constant to provide the flywheel effect. Until recently most of the components needed to run the horizontal department were discrete and the horizontal oscillator coil was easy to find and adjust. But not any more! In the Sharp CX4846, the entire horizontal stage is contained in a single integrated circuit, an IX 0602CE, and there is nothing that even looks like a conventional coil type oscillator. Even the hold and horizontal shift presets are subminiature pots about 6mm in diameter! Even so, unless the designers have come up with some new type of sync pulse horizontal drive, the oscillator still needs a sync pulse and a horizontal output reference pulse. These pulses have to be supplied from other parts of the set and fed into the oscillator chip. So I tried to find them with the scope. This is where I encountered the first major hurdle. This set seems to be an offshoot from VCR technology. The entire circuit board is only about 25cm square and is tightly packed with subminiature and ultra-miniature components. In addition, some of the circuit board tracks are hair-thin and are often completely covered by the printed overlay. This made it almost impossible to trace the tracks and I found that I simply couldn't find the sections I needed without the full service manual. So I advised the customer that his repair was going to take some time and sent away for the needed publication. When the manual arrived, I lost no time in looking up the horizontal oscillator section of the circuit diagram. What I saw made me shudder. There is hardly any part of the oscillator that is outside the big integrated circuit mentioned earlier. Not only that, but many other functions are also enclosed within the chip. There's a complete audio stage, including IF and output; a video IF amplifier, synchronous detector and video amplifier; a sync separator, vertical oscillator, V and H blanking amplifiers, burst gate amplifier and detector; AFC and AGC detectors; and, of course, the horizontal oscillator I was trying to analyse. With so much going on inside the chip, I would not be surprised to find that it was the cause of my trouble. But by the same reckoning, I would expect to see some other JANUARY 1990 61 t l 0 ~ l now had to consider the possibility that it was faulty. It was time to get out the freezer spray. With the set warmed up and the fault apparent, I went over the IC and surrounding components with the spray. Nothing happened. I widened the area of interest, spraying the other chips , various resistors, capacitors and transistors right up to the horizontal output transistor. Still nothing happened. The fault remained and stayed rock steady. Then, after a few days of this delayed onset, the fault decided to revert to its earlier "instant on" pattern. By this time I'd had enough and elected to change the chip. The problem licked I. 1-\i:\"D 1<.a:::.i;.NT"L..'-< INVE-S'1e.D IN A VACUUM DE:SOL-DE:.'RI NG s·n::~,TIONoo• symptoms if it was indeed the chip that was faulty. I had no wish to replace an expensive 28-pin IC until I was absolutely certain that it was at fault. I decided that, before I went that far, I would check surrounding components that might have some connection with the trouble. These components included two electrolytic capacitors attached to two timing circuits inside the chip the phase detector on the horizontal oscillator and the coincidence detector on the horizontal oscillator timing switch. Both of these are 0.47µF 16V units and these small value electros are notoriously unreliable. They were removed and replaced with new capacitors but to no avail. The picture continued to show the horizontal blanking bar - until next morning. At the next switch-on the picture was perfect, without a sign of the earlier trouble. I tried various thump and bump routines but nothing happened for half an hour or more. Then, the picture started to shiver, as if it was about to lose horizontal hold. Finally, the whole picture shifted sideways and locked into the fault condition. 62 SILICON CHIP Two aspects of this reversion to the fault condition led me to think that it might be the chip that was faulty after all. One was the warming up time taken before the fault showed. Admittedly, until now, the fault had been present from cold but I had changed a few components and I had been poking around in the circuitry. This could have led to a slowing down of the onset of the fault. The second indication was that the fault did not snap on but wriggled and shivered for a minute or so before settling down. I still wasn't keen to change the big chip but I TETIA TV TIP GEC 2213A Symptom: No sound or picture. All fuses are OK and there is 320V on the collector of the chopper transistor, TR502. Cure: R503 (22k0) open circuit. This resistor supplies 1 2V to run the chopper control IC and disipates 4.9 watts . The original 5W resistor is rather underrated and a 1 OW replacement will ensure more reliable operation. My usual suppliers had no IX 0602CE in stock and had to place it on back order. I had a week off from worrying about the Sharp before the chip arrived. I had recently invested in a vacuum desoldering station and its value was really shown in this job. In fact, I had the old chip out in two minutes, without the usual struggle and risk of damage to the printed tracks. The new chip went in just as easily and at first switch-on there was no sign of the fault. Repeated trials over the next few days seemed to indicate that the fault was gone. A week later and I was sufficiently convinced to return the set to its owner. There have been no further complaints. When you say it quickly, this job has not been all that unusual. Right from the start the integrated circuit was suspect. But its replacement cost of some $30 plus the difficulty of de-soldering the 28 pins was enough to encourage me to try everything else first. This has been one of those jobs where one wastes considerable time first up but recovers the wastage next time a similar fault appears. And if telling the story here helps you to save some time when you see this fault, then the time has not been wasted after all. Thanks J.L. I think that's enough to keep our readers on their toes for this month. Cheers for now. ~ Speed controller for ceiling fans With summer now in full heat, ceiling fans will be in full swing to keep the household cool. This ceiling fan controller will provide better speed control than most standard controllers. By JOHN CLARKE While those large ceiling fans are very effective in moving large amounts of air, their speed controllers often leave a lot to be desired. Although they may have 4 or 5 speed settings, these can be generally summed up as moderately fast, fast, faster, very fast and terrifying. They don't let the fan run slowly which is what you need, most of the time. After all, you want a gentle cooling breeze not a freezing gale. To solve that problem, we have taken a typical ceiling fan and modified its controller to let it run over a wide speed range from slow to fast. To do this, we have added the Speedi-Watt Universal Dimmer as described in the December 1987 issue of SILICON CHIP. The SpeediWatt reduces the mains voltage fed to the fan motor and thereby controls its speed. It is a phase controlled Triac circuit with electromagnetic interference (EMI) sup_pression components and a snubber We removed the speed switch from our sample fan speed controller and wired a 3-way terminal block in its place. The Speedi-Watt controller was installed in a standard mains power point mounting block. to allow the Triac to safely control an inductive load. Tapped inductor So why aren't the existing fan speed controls effective? We put it down to skimping in the design. Fig.l(a) shows the circuit of a typical ceiling fan with a tapped inductor in series with the motor. For the slowest speed the whole inductor is in circuit while for faster speeds the inductor is progressively switched out. For the fastest speed, position 5 on the switch, the inductor is switched right out of circuit and the full 240V AC is applied to the motor. The reason why the inductor is ineffective is simply that it does not have sufficient inductance. Our modification to the circuit, as shown in Fig .1 (b ), is to wire the Speedi-Watt in series with part of the inductor so that the mains voltage to the motor can be substantially reduced. The inductor and 0. lµF 250VAC capacitor form a filter network which cuts out any buzzing sound in the fan motor caused by the switching action of the Speedi-Watt circuit. Note that our circuits of Fig.l(a) and (b) do not show the details of the fan motor wiring. If you have a look at a typical fan motor you will find that it has quite a bit of external wiring associated with it. This wiring includes a capacitor (generally around 3.5µF 250V AC) to feed the split phase winding and a DPDT slide switch which enables the fan to be reversed. Fig.2 shows the circuit for the fan controller and is identical to the circuit published in the December 1987 issue of SILICON CHIP. It functions in exactly the same way as a JANUARY 1990 63 PARTS LIST 2-WIRE CONTROL 1 Speedi-Watt dimmer (Jaycar KJ-6522) 1 knob 1 3-way insulated terminal block 1 0.1 µF 250VAC capacitor 1 HPM 1 40P standard mounting block 1 HPM 800 blank wall plate 1 metre of 250VAC insulated hookup wire (a) OFF 0 A N SPEED CONTROLLER TO MOTOR ACTIVE OUTPUT SPEEDI-WATT UNIVERSAL DIMMER I 0 0.1 250VAC ACTIVE INPUT Construction ACTIVE MOOIFIEO SPEED CONTROLLER (b) A Fig.1: the original speed control circuit is shown at (a) and used a tapped inductor in series with the motor. The speed of the fan was increased by progressively switching out the inductor. Much more effective speed control can be obtained by wiring the Speedi-Watt Universal Dimmer in series with part of the inductor as shown in Fig.l(b). conventional Triac-based light dimmer (which is exactly what it is). It reduces the AC voltage to the fan by switching on early or late in each AC half cycle. If the Triac switches on early in each AC half-cycle, the power delivered to the load is high; if it switches on late in each half-cycle, the power delivered to the load is low. Now let's discuss the circuit operation in a little more detail. The Active input connects to a single pole switch which is ganged with potentiometer VRl, the speed control. VRl controls the rate at which capacitors Cl and CZ are charged, during each AC half-cycle. CZ is charged to the point where it just exceeds the breakover voltage of the STZ Diac and this then dumps its charge into the gate of the Triac, turning it on. The Diac is a symmetrical device which means that it breaks over and delivers CZ 's charge into the gate of the Triac for positive and negative voltages. This enables it to trigger the Triac for positive and negative half-cycles and thus con64 SILICON CHIP trol the power to the load. So if VR 1 is set for a low resistance, capacitors Cl and CZ will charge quickly and the Triac will be triggered early in each AC half-cycle. VRZ is for fine adjustment and enables the minimum speed to be set for the fan. Rl and C3 form a snubber network across the Triac to protect it from back-EMF voltages generated by inductive loads each time the Triac turns off. 11, a 50µH choke, and C4, a .0lµF 250VAC capacitor, form a filter network to reduce EMI caused by switching of the Triac. S1 -- -- The complete kit of parts for the Speedi-Watt Universal Dimmer is available from Jaycar stores for $9.95. The kit takes the form of a small board which has most of the parts already soldered onto it. All you have to do is solder in the 500k0 switchpot (VRl) and three brass terminals. Solder these in, according to the wiring information provided with the kit and you're almost finished - well, not quite. The next step is to decide how to modify the existing inductive speed control. On some models, you may be able to remove the existing switch and install the Speedi-Watt controller in its place. Alternatively, you may find it easier to wire the Speedi-Watt in its own housing as we did. For this we used a standard 33mm deep mains power point mounting block and matching blank wall plate, as made by HPM or Clipsal. These are available from most hardware stores, Dick Smith Electronics and Altronics . The blank wall plate needs a 10mm hole drilled at its centre. This 1 I TRIAC ACOJF VR2 2M CJ .033 C1 250VAC .047 400V ACTIVE OUTPUT CEILING FAN CONTROLLER Fig.2: a conventional Triac-based light dimmer is used as the speed control circuit. It reduces the AC voltage to the fan by switching on early or late during each AC half-cycle, depending on the setting of VRl. accommodates the mounting bush of the switchpot which is then secured with its supplied nut. Before mounting the Speedi-Watt in this way though, it needs the input and output wires connected to it. These are shown in the wiring diagram of Fig.3. We removed the speed switch from our sample fan speed controller and wired a 3-way terminal block in its place. We then wired the existing speed control and the Speedi-Watt as shown in Fig.l(b) and Fig.3. When installing the Speedi-Watt board on the wall plate, some washers may be necessary behind the plate to prevent the pot shaft and bush assembly protruding too far. We fitted the shaft with a standard 21mm diameter aluminium knob. If you doing a new fan installation, you might consider installing the inductive controller in the ceiling so that it is out of sight. Alternatively, if you are modifying an existing installation, just install the Speedi-Watt next to the inductive controller. Note that when the Speedi-Watt is turned on, the fan will run at full speed. You then turn the knob clockwise to reduce the speed. This is opposite the normal operation for light dimmers but is quite standard for fan controllers and it ensures that the fan starts reliably. Finally, note that the Speedi- INOUCTOR ACTIVE ACTIVE TO SPEEOI-WATT INPUT--....j ACTIVE OUTPUT TO MOTOR Fig.3: here's how to re-wire the existing speed control to include the SpeediWatt. Use 240VAC cable for all wiring and don't forget to insulate the ends of the unused inductor tappings. Watt has an adjustment via trimpot VR2 to set the minimum speed of the fan. To check this, first wind the main control fully clockwise and let the speed of the fan settle down. If that is slow enough, don't worry about adjusting VR2. If you want it to run more slowly, then you will need to adjust VR2. When setting the minimum speed make sure that you don't try and run the fan too slowly otherwise it will tend to stall. The Speedi-Watt is supplied with most of the parts already mounted but you have to install the 500kfl switchpot and the three brass terminals yourself. 0.1 250VAC Warning: don't attempt to adjust VR2 while 240V AC mains power is applied to the circuit. The circuit operates at mains potential and is lethal. Note also that these fans will tend to buzz when operating at very low speed. This buzz is lamination rattle caused by the switching action of the Triac. By using part of the inductive controller as a filter, the tendency to buzz is reduced. ~ This Omega fan is very effective at moving air but runs much too fast in standard form. Our circuit allows it to be slowed right down. JANUARY 1990 65 AMATEUR RADIO By GARRY CHATT, VK2YBX Yaesu's new FRG 8800 • shortwave receiver Just when you thought that you owned the ultimate receiver, a new all singing, all dancing model arrives on the market. You ask yourself just how good is the receiver in my shack? That's what I did when the latest receiver from Yaesu, the FRG-8800, arrived for evaluation. The Yaesu Musen company of Japan has, for years, produced receivers for both shortwave listeners and amateurs alike. Among its offerings over the last 5 years have been the FRG-7 (or "Frog-7" as it was commonly known at the time), the FRG-7000 which like the FRG-7 used the Wadley Loop principle, the FRG-7700 (a PLL synthesised receiver), and now the FRG-8800 which is an even more advanced "semi-professional" receiver. Considering the expense of such receivers, I thought it would •be a worthwhile exercise to do a direct hands-on comparison between the FRG-8800 and its predecessor, the FRG-7700. Computer control Perhaps the most advertised feature of the FRG-8800 receiver is its ability to interface to a computer via an RS232 connection. This feature allows computer control of the frequency and mode of reception, and the selective scanning of any frequencies within the coverage of the receiver (150kHz to 29.999kHz). In addition, there is a facility to enable the "S" meter and squelch status to be recordes by the computer, thus virtually turning the unit into a programmable multimode HF scanner, complete with expanded memories (using the computer RAM or floppy disc). For example, as many shortwave broadcasters use several bands simultaneously for optimum coverage, a program can be written to turn the receiver on at predetermined intervals and test each frequency for signal strength, then select and change the receiving frequency, depending upon propagation conditions, for optimum reception. All this information can be stored in computer memory, providing a log of conditions, frequencies, dates, times and station callsigns. Of course, considerable effort must be expended to minimise the effects of computer generated noise on the receiver itself, but the FRG-8800 is certainly capable of all this, whilst the FGR-7700 is not. Improvements The Yaesu FRT-7700 antenna tuner is a worthwhile optional extra with the FRG-8800. Other optional extras include internal and external VHF converters, a lowpass filter and an active antenna. 66 SILICON CHIP Apart from the CAT (computer aided transceiver) features, it is pleasing to see that Yaesu has improved some of the shortcomings of the FRG-7700. These improvements include wiring the headphone socket so that either mono or stereo units can be used, an enhanced LCD display, a multi-mode squelch which really works and is not limited to FM reception only, a "Woodpecker" noise blanker, memory scanning, and a direct frequency entry keyboard. The direct entry keyboard allows The FRG-8800 can be linked to a computer, thus turning it into what is virtually a programmable multimode HF scanner. The keyboard allows direct entry of the desired frequency. the user to rapidly change from one frequency to another without endless rotation of the main tuning dial, which was an annoying necessity with the FRG-7700. One simply enters the desired frequency in either megahertz or kilohertz directly on the keyboard. Tuning is made easy by the provision of "fast" and "slow" modes, which result in tuning rates of either 125kHz or 6.25kHz per complete turn of the tuning knob. Another improvement in the FRG-8800 is the ability to connect a VHF converter (the FRV-8800) internally. This greatly simplifies antenna connection if using a dedicated VHF antenna and an antenna tuner with the receiver. This applies particularly if it is the genuine Yaesu (FRT-7700), as the wiring when using an external VHF converter (the only type available for the FRG-7700) can become quite a mess! In terms of RF performance, the specifications are little changed. Perusing the specifications for both receivers, it can be seen that the sensitivity and selectivity figures are identical, as are power consumption, size, weight, modes of reception and frequency range. About the only improved specification with any relevance to the actual reception of signals is the receiver stability which is considerably improved at less than 300Hz quoted drift during the first 30 minutes of operation from cold start. Even this parameter is not of extreme importance to shortwave reception. On-air tests On air testing revealed that there were some small differences in the performance of the two receivers when connected to a "long wire" antenna. Perhaps the most noticeable, in the presence of a weak signal, was the slight interference internally generated by the processor in the FRG-8800. This does slightly reduce its ability to recover intelligent speech. The FRG-7700 does not suffer the same problem. However, this inter- r- nally generated noise probably would not cause any significant difference when the receiver is connected to a suitable coaxially fed dipole or Yagi antenna. Eventually the considerations can be simplified to a tradeoff between additional purchase price and enhanced operator features. The FRG-8800 offers all the features that the amateur could want at an affordable price. However, if " no frills" shortwave listening is the ultimate goal it could be that your existing receiver fills the bill. The FRG-8800 is available from Dick Smith Electronics stores around Australia for $1295. The FRV-8800 VHF converter is available for $169. Both units come with a two year warranty. ~ ◄ -- l -~ ►1 \ "Length" In sulator Insulator COAX Cabl e Dipole Antenna A simple resonant dipole antenna will provide fair to good performance over a specific frequency hand. The dipole should be cut to resonate at the centre of the band according to the formula: length (metres) = 142.5/frequency (MHz). JA N UARY 1990 67 _ --- ... --.., ...... -.. ......... ,,, -- .... "' . seen our catalog? Write or phone today for your FREE copy. Over 100 products shown with full details XT 1MB 12MHz TURBO MOTHERBOARD • V20 processor • Can be expanded to 256k, 512k, 640k or 1mb • Uses combinations of 414256, 41464 and 41256 • 4. 77 or 12MHz hardware or keyboard selectable operation • Front panel LED indicators supported • Eight expansion slots e Legal BIOS ROMs included • 8087 maths co-processor capability • Norton SI rating of2.5 • Size 8.5" x 8.5" eweight1.1lbs WAS$129 NOW$110 YOU SAVE! MSS00 - XT 1 MB 12MHz TURBO MOTHERBOARD MINI-TOWER CASE WITH 200W POWER SUPPLY • Metal housing and chassis • Back plate with 8 expansion slots and power supply mounts • Switches on front panel for power, turbo mode and reset • Indicator for power • Keyboard lock with 2 key set e Will hold 2x5.25" half-height and 1x3.5" third-height drives • All necessary hardware included • 7.5"wx 16.15"0 x 12.75"H eweight22.5Ibs H3525 - $299.oo MIDI-TOWER CASE WITH 200W POWER SUPPLY • Metal housing and chassis• Back plate with 8 expansion slots and power supply mounts• Switches on front panel for power, turbo mode and reset • Indicator for power, turbo mode and 2 x hard disk indicators • Keyboard lock with 2 key sete Will hold 3x5.25" half-height and 1x3.5" third-height drives • All necessary hardware included e 7.5"Wx 16. f 5"0 x 1?"H e Weight24.5Ibs H3521 - $349.oo MAXI-TOWER CASE WITH 220W POWER SUPPLY e Will fit AT/386 Baby or Full (standard) size motherboards• Space saving floormount case• Metal housing chassis • Anti-static coated plastic face plate • Back plate with 8 expansion slots • Switches for Turbo and Reset • Indicator lights for Power, Turbo mode, Hard Disk (1 &2) operation • Keyboard lock with2-key seteWill hold up to a combination of 6 half-height floppy or hard disk drives• All necessary hardware included e Colour bei()e e 7.35"W x 16.75"0 x 25.25" H • Weight 34lbs HJs20 - $499.oo OUSE The cordless mouse is a "pointing device" for drawing graphics, moving objects on screen and picking up items simply by moving the mouse on the chosen item and pressing a button. Unli.ke most of the other mice, the cordless mouse uses the latest Infra-Red signal transmission technology. Comes complete with driver software, test program and menu maker. COLOUR GRAPHICS ADAPTER FOR IBM PC/XT/AT The M5752 is a colour graphics adapter card capable of operating with either IBM RGB or composite monochrome monitors and features the following: • Parallelprinterport • Text modes: 40 x 25 or 80 x 25 • Graphic modes; 320 x 200 or 640 x 200 • Light pen interface • Includes composite video monitor adapter • Manual included Ms152 - WAS $115.00 NOW $89 H3955 INFRA-RED MOUSE - $169.00 PC/XT 150W POWER SUPPLY GAME CARD • • • • • Two port Runs two joysticks M 5850 wAS $29 .50 NOW $25.00 e e e Input <at>47-63Hz (1101240v switchable) Output +5V<at> 15A, -5V <at>0.5A, + 12V <at>5.5A,-12V<at>0.5A Plug compatible connectors Buiftin fan Size 5.5"w x g_5"d x 4.625"h Weight 6Ibs H3730 - WAS $125.00 NOW $89 2MB RAM CARD FOR PC/XT/AT Memory expansion for the PC/XTIAT, frees users from the aggravating drawbacks of the 640K MS-DOS limit. It fully supports both the Lotu&'lntel/MicrosoftExpanded Memory Specification (EMS) and the AST/Quadram/Ashton-Tate Enhanced Expanded Memory Specification (EEMS). It allows multi-tasking programs such as OESOview to acess its up to 8 MegaBytes of memory. Software for backfilling conventional memory to 640K Is also included. FEATURES Supports EMS 4.0. Enhanced Expanded Memory Specification. Up to 2 MByte of expanded memory per card using inexpensive 41256 dynamic RAM chips. Up to 4 cards are allowed to use in one AT or XT. Supports DESQview, Framework, Lotus 1-2-3 and Symphony. M5982. PrintBuffer, TurboOisk Ramdisk and backfilling software provided. $245.0Q COMPUTER PART# SIZE AMIGA AMIGA AMIGA D2930 D2932 D2938 3.5" 5.25" 3.5" CAPACITY 880K 360/880K 880K COMMENTS PRICE WITH ON/OFF SWITCH WITH ON/OFF SWITCH INTERNAL KIT FOR A2000 249.00 299.00 229.00 AMSTRAD D2904 3.5" 720K FOR PC1512/1640 269.00 ATARI ATARI D2916 D2918 3.5" 5.25" 720K 360/720K WITH POWER SUPPLY SWITCHABLE, WITH POWER SUPPLY 269.00 299.00 IBM IBM IBM IBM D2946 D2948 D2950 D2952 3.5" 3.5" 5.25" 5.25" 720K 1.4MB 360K 1.2MB WITH WITH WITH WITH 299.00 329.00 299.00 329.00 TOSHIBA TOSHIBA D2970 D2972 5.25" 5.25" 360K 1.2MB SUIT TOSHIBA LAPTOP SUIT TOSHIBA LAPTOP 349.00 399.00 ZENITH ZENITH D2976 D2978 5.25" 5.25" 360K 1.2MB SUIT ZENITH SUPER SPORT SUIT ZENITH SUPER SPORT 349.00 399.00 COMPAQ COMPAQ D2980 D2982 5.25" 5.25" 360K 1.2MB SUIT COMPAQ SLT 286 SUIT COMPAQ SLT 286 349.00 349.00 ADAPTER ADAPTER ADAPTER ADAPTER INTERFACE INTERFACE INTERFACE INTERFACE & & & & CABLE CABLE CABLE CABLE ALL TOSHIBA/ZENITH/COMPAQ DRIVES INCLUDE EXTERNAL POWER SUPPLIES, INTERFACE AND CABLES WE ALSO HAVE A RANGE OF DRIVES FOR OTHER BRANDS SUCH AS APPLE AND MACINTOSH AS WELL AS A RANGE OF BARE DRIVES IN 360K/720K/1.2MB/1.44MB/2.88MB FORMATS e NEW PRODUCT COMING SOON - 512K RAM CARD FOR AMIGA PHONE (02) 418 6711 FAX (02)4186713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 FREIGHT CHARGES Include $10 with order for all normal items - heavy items, e.g. monitors add $15. 14 day money back guarantee Order by phone (use credit card). by fax or by mail. Unless insurance is declined it will be charged at 1% of tota l purchase. This is for your protection. PRICES VALID AT 1 DEC 89 DEALER ENQUIRIES WELCOME COMPUTER BITS By JENNIFER BONNITCHA Speeding up your PC Is the trend towards bigger/newer/faster computers starting to get you down? Are you one of the early PC owners worried that you are getting left behind in the speed/storage race? Fortunately, there are several alternatives to "junking" your old PC and moving up to the more expensive models. the options store many programs and the associated data files. In addition, the time saved in shuffling discs into and out of the drives can be quite significant. If your software uses the disc drive intensively, your best bet is a fast hard disc with around 28 milliseconds access time. Cache memory There are many ways to help you catch up to the leaders. You can use hardware products to add to a low-end computer's memory, or increase its computing power. Or you can use better software. Some companies, such as Borland International with its Quattro spreadsheet, take an alternative approach by designing software which is very powerful and yet tolerant with disc storage and memory requirements. Other programs like Mace and Norton Utilities give you the ability to fine-tune your computer system. It used to be so easy. A PC came with a maximum of 51 ZK memory and all programs could easily run within this limit - you even had enough left over to run memoryresident programs like SideKick. As times changed and the much faster, more sophisticated programs required more memory, it became obvious that something had to be done. Apart from the obvious enhancement of more memory, for around $350 you can buy a hard disc drive to accommodate programs too large for standard floppy discs . A hard disc has enough room to You could try using disc caching software which sets aside a portion of RAM as a temporary storage area - or cache. This means that when a call is made by the software for data, the cache software intercepts the call, locates and passes the data to the program, and stores as much as will fit in the cache. Should the program require the same data again, it is available immediately. Interestingly, as you work, the program continues to monitor the data required and places as much as possible in the cache, even if it was not the most recently used - smart eh? It should be apparent that a program this clever could help speed up even the slowest application. Typically the cache is used when dealing with very large data files such as those generated by database and spreadsheet programs. RAM discs ONE WAY OF SPEEDING UP your PC or PC XT is to add an accelerator card with its own 80286 or 80386 microprocessor. You just remove the cover and install the board according to the supplied instructions. This 286 accelerator card from Electronic Solutions runs at 8MHz. 70 SILICON CHIP Another alternative is the RAM disc (or VDISK with DOS 3). Using this technique, a portion of RAM is made to act as though it is a disc drive. You copy data into the RAM disc and access it just like the familiar hard disc. In this case, you decide what is available whereas cache software decides for you. The main advantage of the RAM ADDING A RAM CARD allows you to create RAM discs and use memory-resident utilities to speed up your work. This EEMS RAM card lets you expand the system memory by up to 2Mb. (Available from Electronic Solutions or PC Marketplace). disc is increased response time but the downside is that anything stored in RAM is subject to loss whenever power is lost to the computer. You still need to transfer data from RAM to a disc for permanent storage. A popular trick is to copy program overlays, dictionaries etc onto a RAM disc to speed up the operation of programs which make extensive use of overlays. Or how about an Accelerator card, which includes its own 286 or 386 microprocessor? Generally, you will experience increased speed from your ageing companion. You just remove the cover, add the board and hey presto, supercharged operation! Alternatively, you could opt for a faster processor chip. The original PC limped along at 4.77MHz to make sure all other parts of the computer system could keep up with the pace. To speed it up, the PC can make use of the NEC V20 and V30 processor chips. The V20 is for use in 8088 computers and the V30 in 8086. The main function of these chips is to speed up some, but not all, operations. Maths co-processor Speaking of processors, if you spend a lot of time dealing with numbers, you may consider a maths co-processor. This little chip slips comfortably onto the motherboard of almost any PC since most are manufactured with the empty socket. The 8087 maths coprocessor certainly speeds up number crunching activities like calculating square roots and drawing screen graphics in programs like computer-aided design (CAD). Most PCs run on some version of Microsoft's Disc Operating System (DOS). This system controls all basic operations for the computer so some developers have found ways to modernise this operating system. IBM recently released a new single user, multi-tasking operating system known as OS/2, also designed by Microsoft. Software is specially designed to take advantage of the OS/2 facilities in that each program is similar in operation, in much the same way as the Macintosh computers. DOS has now been endowed with some of the OS/2 characteristics through programs like DESQview and Windows which feature the increasingly popular graphical interface. Both these programs enable a standard PC to run several programs at the same time and work with larger amounts of memory than is usually allowed with DOS. Windows in particular is designed for the 286 machines and better, however it can provide the more powerful versions of 8086/8088 computers with some of the graphical interface. Another multi-tasking operating system option is Unix/Xenix, however these tend to work best on the 386 machines. Speed junkies can add memory and speed-up boards to their old PC workhorses, however it is important to understand a few basic principles. Expanded memory The original vanilla-flavoured PCs don't function particularly well with Windows and they certainly aren't capable of running the new OS/2 operating system. An alternative for machines with 8088 or 8086 processors is expanded memory which conforms to the Expanded Memory Specifications used by Lotus, Intel and Microsoft (sometimes referred to as LIMS memory). With expanded memory, you can obviously work with much larger data files but you can also use memory-resident utilities and RAM discs to speed up your work. Whenever the computer calls information from a disc, there is a delay while the operating system checks the File Allocation Table on the disc to determine the exact location of the data. Calling the same information from a RAM disc is astonishingly faster. If this sounds like the alternative for you, all you really need is an 8-bit expansion slot in your computer and a memory board which will fit into the case. ]ANUARY1990 71 Speeding Up Your PC - ctd THIS HALF-CARD will allow you to increase the RAM in your PC out to 640K. (Electronic Solutions & PC Marketplace). The AT-style computer released in 1984 features the 80286 processor running at around 8 to 10MHz. Once again, you can make use of the features mentioned above to really add some zip to your computing. Additionally, you can use DESQview or Windows/286 to run several programs at once and work with the larger amounts of memory. Finally, let's look at the 80386, which has memory management inbuilt. Should you feel the need to really zap along, you should add full-speed RAM to the mother board or in a 32-bit expansion slot. Addressing over 640K A generally little-known fact a bout the 8088 and 8086 PCs is the ability to address 1Mb of memory. Since the maximum addressable by DOS is 640K, the remaining 384K is used by the CPU iteslf to find data or instructions. From 640K to 768K is reserved for video drawing and re-drawing instructions. Hard disc controller ROM modules typically 72 SILICON CHIP use from 768K to 896K, while the PC's own ROM will address from 896K to the 1024K (1Mb) limit. But no matter how hard you try, you can't use the top 384K of memory using DOS. Sometimes, on AT-style computers, the additional memory is used as "shadow" memory. A copy of the ROM BIOS is loaded into RAM for increased performance. Shadow RAM can also enhance the screen refresh on EGA monitors. While the 8088 addresses 1Mb of RAM, the 80286 can address up to 16Mb and the 80386 a staggering 4 Gigabytes (ie, 4,096Mb)! While the space below 1Mb is used by various sections of the computer, the space above 1Mb is reserved purely for extended memory. It is here that operating systems like OS/2 and Unix use the additional space for vastly increased computing power. However, whenever the 286 or 386 computer runs DOS, it has the same problems as the 8088 - the 1Mb address limit. Extended memory lets DOS use 64K to bring it up to 740K. Windows/286 supports this added extra. Users of the 80286 and 80386 machines can actually choose between expanded or extended memory. When considering the purchase of a memory board, you should aim for a board with supports a variety of configuration options - conventional, extended and expanded (preferably with software rather than hardware selection for ease of use). Extended memory is typically used for programs such as OS/2 and Unix since they require a fair amount of room to move. But as far as DOS is concerned, extended memory is really a dead end. Expanded memory on the other hand provides a much greater data space and manages multitasking sessions. The increased data space means you can create larger spreadsheets and move your utility programs to expanded memory. It relies on a feature known as "paging". A "window" within the visible memory area (1Mb on the 8088) is swapped to different areas or "pages" within the expanded memory. Thus the CPU is fooled into operating within the virtual area created by expanded memory. Above 784K, there is 64K of empty space in an unused memory gap. Expanded memory can therefore create a page frame to hold at least four 16K pages. By managing the CPU requests, the memory manager can map any 16K segment within expanded RAM into any of these pages. None of this happens automatically. Expanded memory relies on both the hardware and software working together. A combination of extra RAM, memory mapping hardware on the board and a device driver in your CONFIG.SYS file all work together to let your applications and DOS recognise the paged memory. So the moral of the story is that those programs that work well at the low end of the computing scale perform even better at the high end on the more powerful machines. But as long as there are ways to keep these older computers kicking along, the plug need not be pulled on low-end boosters. ~ REMOTE CONTROL By BOB YOUNG Designing UHF transmitter stages Last month we dealt with the simple transmitter for use on 27 to 40MHz, typically using a 3rd overtone crystal and one or two stages of straight amplification. This month we 'II discuss a much more ambitious transmitter operating on UHF. Many radio control applications call for transmitters using ultra high frequencies and this requires some very clever electronic circuitry. Here in Australia, DOTC licenced users are allocated eight spots in the 471.225 to 471.8MHz band for industrial R/C. Over the last three months, I have been totally engrossed in the development of a low power 471MHz Tx and Rx for use on this band and the cleverness called for has been driven home to me in no uncertain manner. My 26 years in electronics have all involved working between 27 and 40MHz, which meant that I was constantly required to devise ways to avoid introducing harmonics in the Tx output. Now, I suddenly found myself in a situation where strong harmonics had to be deliberately introduced, not just into the Tx output, but into the very OSCILLATOR FET BUFFER AMPLIFIER early stages of the transmitter. Not only that, but UHF and above are very difficult bands to work with. The very first thing that you learn when working on these frequencies is that there is no such thing as a short circuit. A shorting bar across a lOpF trimmer has appreciable inductance and therefore tunes beautifully. So minaturisation and UHF go well together. However, if you are producing prototypes, it can be very frustrating. While feeling very sorry for myself in the middle of researching this project and asking myself that perennial question, "How did I get myself into this one?", I was pulled up with a jolt by a reference to Marconi conducting most of his early coded transmissions on 800MHz. It was not until he went after distance that he came down to the lower frequencies. Once again I f X3 IX 6 TRIPLER DOUBLER OSCILLATOR FET BUFFER AMPLIFIER (a) OSCILLATOR BUFFER was made forcibly P' vare of the cleverness of those r _.y pioneers. There was no slipping around to Dick's for silver mica capacitors, lifting the lid on a UHF CB to see how they did it there or checking the output on a Marconi Test Set, spectrum analyser or digital frequency meter for those people. All they had was their genius, a sound grasp of mathematics and unsurpassed determination. What components they lacked, they designed and made. Those people, the people who followed and the present generation who work in this very difficult area of electronics have my utmost respect. Features of 100mW NBFSK Tx Fig.1 shows the block diagrams of three typical 100-500mW UHF transmitters intended for use in industrial radio control. As this is not a construction article, only the broad principles will be discussed. The circuit diagrams discussed in many cases have all of the bias, decoupling and idler circuits removed for clarity of the principles involved. Do not attempt to build these circuits, as they won't work. Ix 3 Ix 6 TRIPLER DOUBLER (b) MODULATOR AMPLIFIER Ix 3 IX 6 IX 6 Ix 6 TRIPLER DOUBLER AMPLIFIER POWER AMPLIFIER (c) Fig.1: these block diagrams show three different approaches in designing UHF remote control transmitters. Note that the oscillator output frequency (f) has been multiplied by six in each case to achieve operation at UHF. JANUARY 1990 73 to 3kHz deviation whereas the "foldback" receivers such as the Philips 2033 and 2050 require plus and minus 4.5kHz for correct operation. Thus our choice of crystal/ oscillator circuit is heavily influenced by these requirements. Actually, the final decision on crystal type is virtually forced upon the designer by the limitations in crystal technology. Most manufacturers in Australia are limited to overtone crystals in the 100-150 MHz range, a figure well short of the required 471MHz. The difference must therefore be obtained from the frequency multiplier stages which follow the oscillator. Deviation & stability Want to control a concrete pour by remote control? No problem. This industrial grade UHF transmitter gives an operator full control of the concrete truck shown above. At right is the view inside the unit. For each of the circuits of Fig.1, the chain commences with the oscillator. As this Tx is intended for low cost, low range NBFSK (narrow band frequency shift keyed] applications, a simple varicap diode is used as a modulator. There are several problems to be considered in the choice of crystal and hence the oscillator circuit. To begin with, DOTC specifications for the VHF/UHF bands usually call for maximum deviation of ± 5kHz on the carrier frequency. Added to this, we have a responsibility to other users to use the minimum spectrum space that modern technology allows. At least this is one problem Marconi never 74 SILICON CHIP had. There were not too many users of the radio spectrum in those days. In addition, NBFSK receivers can require anything from a single shift of plus or minus 1.5kHz to a double shift of plus and minus 4.5kHz deviation for reliable results. The smaller the deviation, the worse the signal-to-noise ratio. Even the full deviation allowed by DOTC results in a poor signal-tonoise ratio and this is one of the shortcomings of NBFSK. It is not until true FM (frequency modulation] is employed, with deviations of ± 50kHz and over, that good signalto-noise ratios are obtained. Typically, most conventional NBFSK receivers require from 1.5 Here again a problem is introduced with regard to the oscillator design. Any frequency shift in the oscillator will be multiplied by the frequency multiplier. Thus, since we need only 5kHz deviation, the maximum oscillator shift is only 833Hz (oscillator frequency 7 6). As we have seen, good results can be obtained from most modern NBFSK receivers at 2kHz deviation, leaving some margin for drift at the transmitter end. In fact, a well designed Rx with a narrow bandwidth will begin to reject deviations greater than 2.5kHz. Once again we see the continual compromise that designers are confronted with. The multiplier stages also magnify the problems of crystal stability and tolerance. Thus, a crystal rated at 5 parts per million will give a final result of 30 parts per million when followed by a 6-times multiplier stage. Because of the very narrow frequency shift required, an oscillator that is very difficult to pull off frequency will give good results in this application. A series mode overtone Colpitts circuit (Fig.2) fills this requirement nicely. Overtone crystals can be cut up to 150MHz reasonably cheaply, depending upon the temperature stability required, and will typically only pull a maximum of 1-1.5kHz. Fundamental crystals are more expensive to cut and this cost escalates above 26MHz, again depending upon the temerature +4-1sv--------~ C4 1-o~w~J II ;rC4 L2 l 1 L1 INTO HIGH IMPEDANCE ~ ~ CJ -:-- Fig.2: this series mode overtone Colpitts oscillator circuit is ideal for use in NBFSK transmitters. Note the tuned collector load for Qt which multiplies the output frequency. r"t?f ·J ::r~t r (a) R1 Fig.3: typical varactor diode frequency tripler circuits. Fig.3{a) utilises an L-section matching network while Fig.3{b) uses an output transmission line matching circuit. coefficient required. However, they will pull much more readily typically from 2-4kHz. The situation for NBFSK R/C model transmitters working on the 27-40MHz bands is quite different. Because the gap between crystal frequency and the output frequency is much smaller, high multiplication factors are not necessary. Radio control transmitters on the 2740MHz bands usually use a fundamental crystal on f/2 (second harmonic) in order to get the required frequency deviation. The required frequency doubling usually takes place in the oscillator output tuned circuit. This approach is cheaper and more reliable than adding high orders of multiplication. I find the conditions under which the crystal is expected to work the big objection to NBFSK modulation as compared to AM (amplitude modulation). In AM, the crystal locks the electronics to the required frequency whereas in NBFSK, the electronics hold the crystal on frequency - a real cart before the horse situation to my mind. In addition, great care must be exercised in matters such as voltage regulation and component stability in particular. The fact that the system works as well as it does is a credit to the modern component industry. Added to this, NBFSK sets are more difficult to service, more expensive to re-crystal and give signal-to-noise ratios in some cases, depending upon the Rx design, much worse than the AM sets. The only genuine advantage that I can see is that NBFSK can be used to transmit the more complex data streams used in PCM sets. For the average flyer, car and boat enthusiest, the AM PPM set is still the most reliable and cost effective unit available. Frequency multipliers Frequency multiplier circuits are intended to generate harmonic signals from the fundamental input frequency. Transistor and FET multipliers will generate usable harmonics up to the 6th although the most commonly used multipliers are doublers and triplers. This is because efficiency falls off very rapidly after the third harmonic. Diodes also work quite well as frequency multipliers (Fig.3). Varicap or step recovery diodes are used at lower power levels while varactor diodes are generally used at power levels above 100mW. If the efficiency is not critical, conventional silicon epitaxial switching diodes may also give good results. The correct choice of transistor is very important in multiplying amplifiers. Many RF power transistors have a significant collectorto-base capacitance that is not directly underneath the emitter "fingers". Most of the series resistance into the base region (rbb') is therefore bypassed and a fairly high quality varactor diode thus exists, the capacitance of which changes with collector-tobase voltage. When used as a frequency multiplier, this transistor can provide noticeable improvements in power gain and efficiency, particularly when used near its upperfrequency limit. The theory of frequency multiplication is very simple and illustrated in Fig.4. In essence, all that is required is to introduce a controlled amount of distortion into the input sine wave. Any nonlinMr amplifier will generate harmonics in the output waveform, however the trick is in the amount of control exercised over the level of distortion. The drive level and bias applied to a multiplying amplifier are quite critical. If the input drive is insufficient to overcome the negative bias, the stage will not function at all. For this reason a preamplifier stage JANUARY 1990 75 vcc Fig.4: a class C frequency tripler, together with its input and output waveforms. The tuned output circuit filters out the unwanted harmonics and provides a flywheel effect at the desired frequency. between the oscillator and multiplier is often desirable. In effect, a frequency multiplying amplifier works in class C. The output is clamped off with a diode to allow the correct level of ringing to take place in the output LC network. The tuned circuit in the output then acts in two ways. First, it provides the necessary filtering of unwanted harmonics and second, it provides a flywheel effect at the desired frequency. Thus the stored energy in this resonant circuit generates the fill-in waveform (when the transistor is not conducting) at the required harmonic frequency. In practise, working with multipliers can present quite peculiar problems and a spectrum analyser is virtually a must. Parasitic oscillations (spurious oscillations occuring at unwanted frequencies) are quite a serious problem in all transmitters and even more so in the VHF/UHF bands. Actually, this is fundamen- tal to the vast difference people find in working with transmitters as against receivers. In a receiver, the power goes up as the frequency goes down, whereas in UHF transmitters, the power goes up as the frequency goes up, presenting the worst possible scenerio for parasitic oscillation. There are many ways to prevent parasitic oscillations and any good UHF book (ARRL Handbook or Jessop's VHF/UHF Manual) will outline the techniques which include the use of ferrite beads, base stopping resistors and neutralisation. Neutralisation Mosfets have big advantages over bipolar transistors when used as RF amplifiers. In a transistor there is a feedback path from the collector to the base which can be adequate to sustain oscillation within the circuit. The method used to eliminate or neutralise the feedback path is called 'unilateralisation'. By comparison, a Mosfet has a very low feedback or reverse transfer capacitance so no special neutralising circuitry is required. This represents a very big saving in production costs, particularly in circuits such as push-pull and pushpush multipliers as shown in simplified form (ie, without unilateralisation) in Fig.5. These two circuits are very interesting as they have some degree of harmonic cancellation, the pushpush circuit amplifying the even harmonics (2nd, 4th and 6th) and attenuating the odd. Conversely, the push-pull circuit amplifies the odd harmonics (3rd, 5th and 7th) and attenuates the even. Fig.6 shows the push-pull version using Philips BSD 12 N-channel Mosfets. The BSDl 2 is a very fast switching device which gives good results as a multiplier. Note that electrical balance and symmetry are important in this type of circuit. The FETs are self-biassed with a pot between the sources providing a balance control. Correctly set up, this circuit will give a good clean output at 471MHz with all harmonics over 30dB down. One very interesting device which I found after I had completed the 471MHz project, and therefore have not tried personally, is the Motorola MRF629 tripler. This transistor is nominally a 2W 9dB gain 470MHz 12.5V amplifier assembled in a TO-39 common (grounded) emitter case. A unique feature of the chip is a pair of diffused Faraday shield diodes which help isolate the common-emitter input from the output. These shield diodes are electrically connected across the output-collector to. emitter by very 3f [ ] (a) Fig.5: typical bipolar transistor frequency multiplying stages. Fig.5(a) shows a push-pull tripler circuit, while Fig5(b) is a push-push doubler arrangement. Both circuits are shown without neutralisation. 76 SILICON CHIP +10V ..,. result in an unstable and noisy Tx output. Once the stage is tuning smoothly and correctly, replace the large trimmer with one that tunes only over the range of the required harmonic. Output stage Fig.6: push-pull tripler circuit using Mosfet transistors. Mosfets have very low feedback capacitance so no special neutralising circuitry is required. short interconnected feed bars. When properly biased, they act as shunt varactor diodes which are able to multiply frequency. Thus, one can design an amplifying multiplier in the stable commonemitter configuration using the simple shunt diode networks usually associated with common-base designs. This device will produce 700mW at 450MHz from a 150mW 150MHz input using a supply voltage of 9-10V DC. The circuit tends to operate in a nearly saturated mode. This keeps the collector current almost constant and thus makes power supply regulation relatively easy. Tuning a multiplier stage Tuning a multiplier stage should present no problems. A correctly working multiplier which has a sufficiently large trimmer capacitor will tune the centre frequency and one harmonic on either side. Thus, a tripler with the trimmer fully engaged (ie, at maximum I I STRONG PARASITIC capacity) will first peak the 2nd harmonic then, as the trimmer is slowly moved towards minimum capacity, the 2nd will fall in amplitude as the 3rd increases. Continuing towards the minimum position, the 3rd will peak and begin to fall as the 4th begins to peak. Thus you should be able to exercise complete control over each harmonic with the tuning smooth and free of sharp or abrupt rises or falls. Should the entire frequency comb rise and fall in unison (eg, the trimmer is acting as if it were an attenuator), then suspect an earth loop or some similar problem. Always keep a close watch for any evidence of parasitic oscillations [a spike out of step with the spacing of the comb, as in Fig. 7) and in particular triggered regeneration. This is a special case in which a parasitic very close to a harmonic locks itself to that harmonic and gives an amplitude peak that is completely out of character with the rest of the comb. This can I I TRIGGERED II piiA:/JIC II II II II I I II II II II II !l 10 2IO 3IO 4IO ~ 5IO Fig. 7: when tuning a transmitter, always watch for evidence of parasitic oscillation. This frequency output spectrum shows a strong parasitic oscillation between 3fo and 4fo and a triggered parasitic which is locked to 5fo. The output stage is fairly routine, if anything at UHF could be said to be routine. The main considerations for this stage are efficiency, harmonic filtering and matching the output transistor to the antenna. The question of cost, efficiency and harmonic filtering are closely related. If the harmonics have been filtered at each stage [where they are much easier to attenuate) and the driver presents a nice clean input to the power amplifier (do you refer to a 100mW stage as a PA?), using class C bias will only reintroduce the harmonics as we have already seen. However, if it is decided that the doubler and PA stage are to be combined, in the interests of reducing cost, then class C bias is a must. Fortunately, a good output network will serve to match the antenna as well as attenuate any reasonable number and level of harmonics to the level required by DOTC. If your application can stand the loss of efficiency, class A bias will give a clean, harmonic free output, requiring the minimum of filtering. One of the nice things about UHF is the size of the antennas. As the wavelength is only 63cm at 471MHz, a quarter wave antenna is only about 15cm long. Compare this to the 2.54-metre long quarter wave antennas we used on our first ground based 27MHz single channel transmitters. Using good antennas on a 1W 471MHz RF link will give R range of about 40 kilometres over water. But potential R/C users should be warned: on land, UHF is very different. The 63cm wavelength is very reflective and, when used amongst steel girders and over land, can give quite misleading results, with dead spots showing up in the oddest places. Note also that this band is only available to DOTC licenced commercial users. ~ JANUARY 1990 77 of these quality produ TOLL FREE on 008 - 9 Country Jack O'Donnell Managing Dirtector Audio Frequency Generator , ____ I GREAT DUAL TAPE \ SAVINGS I ONE RING to AC I Many combln 300 WATT INVERTER L.----J WITH AUTO START Operate, from 12V Car Battery • Auto Start draws power from your battery only when appliance is plugged in and •turned onN ie, battery can be left permanently oonn,cted if required.• Voltage Regulated• Current Regulated • Current Overload unit self limits Complete Kit In testing audio circuitry it is necessary to have an accurate audio signal source. It even allows you to test 455kHz IF stages! Features: • Outgoing lff:ssage variable from 30 to 120 sr:c. • Amiouncement-only mode • Incoming message is voice controlled • Incoming call can be monitored • Rapid erase • Has built-in microphone - great for dictation A 0512 Normally $199. This month 50 only at $149 (No back orders at this price) SPECIFICATIONS: Frequency Range Accuracy Output Waveforms Output Level K 6750 $279.00 Fully built and tested 10Hz .1MHz +/-3% +2Hz Sine/Square Sine:8VRMS Square: 10V P-P -20db, -40db Output Attenuator and fine adjust Q 1540 Normally $299 This month $249.00 SAVE $SO Beat Triggered Strobe Add more life to your next party/ Flashes in time to your music, or as nonnal strobe. Exclusively customised by ALTRONICS ~ into our H 0480 Instrument Case. Includes silk~~ •=ened panel. .~ ti,.\.; K 5790 Was $79.95 Now $75.00 (See AEMJuly'85) K 6755 $379.00 POWERHOUSE 6QOW INVERTER (SeeEA Dec'87) This in~rtcr has the capacity to produce 600 watts of mains power which will run a fantastic array of appliances. Ideally suited to rurming power tools, lighting (including fluros) electric motors and much more. It can be used eith;r u a portable or a pennanent fixtw'C. • Manual or Auto Start facilities • Low battery cut•out. Kit version K 6770 $425.00 ,~\I Fully built and tested 12V Input K 6774 24V Input K 6775 $525.00 Tube Option K 5795 $16.50 Now $15.00 100'5 OF USES AT HOME AND AWAY • ·; · , 1 ..,.. ~ •_"' ,-;-1-IE 1 ' }l°ES't BONUS OFFER We will include a set of 4 Car Alarm WARNING stickers ($3.95 value) ABSOLUTELY FREE with every Car Alarm Kit ordered this month. The Protector Alarm Kit Toroidal Power Transformers Features: Internal & External Sirens Dash Lamp Flasher Battery back-up Delayed and Non-delayed inputa Easy to build and install 87 diam. 40mm H, 1, 1kg, leads 200mm Cat No. M3020 M3025 M 3030 M 3035 M 3040 Sec. V. 12+12 18+18 25 +25 30 +30 35 + 35 160VA (Watt) Models K 4370 Was $129.00 at $119.00 SCREECHER CAR Why a Toroid? • Smaller size and weight to meet modern "Slimline" requirements • Low electricity induced noise demanded by compact equipment. • High efficiency, enabling conservative rating whilst maintaining size advantages • Lower operating temperature • Simple, quick, single bolt mounting. Normally $65 This Month $59 Cal No. M 3050 M 3055 M 3060 M 3065 M 3070 M 3071 M 3075 M 3080 Sec. V. 12 +12 18 + 18 25+25 30 + 30 35 + 35 35+35,15 + 15 40 + 40 45 + 45 125 diam. 45mm H, 2,5kg, leads 200mm (See EA Aug '86) Ear Splitting 11 Odb Modulated Tone Now our top selling car alarm. Two sensor inputs • normally open and norma ly closed, enable simple connections to door, bonnet, boot light, switches etc. Great Value $39.95 110 diam. 45mm H, 1.8kg, leads 200mm 300VA (Watt) Models ALARM K43so Primaries 80V A (Watt) Models Normally $55 This Month $49 (See SC Feb '88) This refined car burglar alann has about every feature you could possibly want to keep would·bc thieves away. NOW a GREAT SPECIAL These are the genuine Grain Oriented Toroid Transformers as used In Electronics Australia and SI/Icon Chip Magazine Projects. Normally $79 This Month $69 • CaL No, M3085 M3086 M 3088 M 3090 M 3092 Sec.V. 12+12 18+18 25 + 25 30 + 30 35 + 35 M3100 40+40 -::====::::=---------, r --·..................... Superb RedfordWireless Microphone ! System Uses Dual Diversity Receivers 1 for long Range, Noise Free, Pure Fidelity Reproduction. HAND-HELD MICS. )/ Breathtaking performance without signal drop-out or noise interference. The Redford Wireless System is virtually the ultimate in an Entertainer's Microphone System (or for any roving microphone application for that matter!) All the annoying wireless microphone STANDARD MIC. co122 $349.00 SHURE SM58 INSERT / (use with C 0122) Dynamic Range exceeding l00db is obtained by employment of a patented special Parabola level compressor and dynamic expander. Please Note: 4 different operating frequencies are available ( you will need to specifically no,runate a desired frequency C0142 $259.QQ only if the equipment is being used in proxi,ruty with other SHURE Redford systems on the 200MHz band. Please specify if you MIC.COMPLETE FEATURES: have preference. characteristics such as "drop-out" , static • No dangling Antenna or Microphone to Freq. available: 202.1MHz, 202.4MHz, 202.5MHz and and noise are completely eliminated by use get in your way • High Dynamic Range 203.7MHz of auto switching dual diversity • Standard "AA" Batteries give long ROAD receivers. The output of each receiver is powerful operation • Advanced co12a $575.00 CASE continually monitored, with the strongest Technology - Automatic Switching Dual and clearest signal alw~ys selected. Diversity Receiving System. co112 $729.OO Portable PA System with inbuilt Dual Diversity Microphone Receiver The operating range Is a minimum of SO Just released, our powerful 50W RMS, wide range amplifier speaker system with inbuilt diversity wireless mic. receiver. Fantasic for outdoor and indoor function., where high quality sound and fade free wireless microphone is required. Ideally suited for auditoriums, sporting arenas and dance halls. Will accept a tape recorder or input and reproduc.e quality music. The unit operates on 240V AC mains m ANTENNA C0160 SAVE $400 Fantastic for aerobics groups. This high grade system sells elsewhere for $1290 - $79.95 Altronics introductory price - only $899 be root C 0103 (202.4MHz) C 0105 (203.7MHz) Extension Antenna can Microphones - use any ofthe Redford UllF Wirekss microphones or Guitar Pick-up with this system. (Mie. not included) Passive Infra-Red MEGGER METER Sec EA April/May 89 Lite Guard Insulation breakdown can in electrical wiring and appliances can be determined with this dual range megohm m::tcr. Floodlightl:'·Control ) How often have you thought there could be a prowler :: / ) outside your door? Install a Lile Guard & (once armed) · :•,:':'.':/ /':':' any "guest" will be floodlit when detected by this highly · · · · · · · · · sensitive Infra-Red Detector. {(//{fi. Speclflcatlons: • Ralntlght, outdoor, all weath:r operation • \))} \ )_ Operation Time: Adjustable l-20mins • Sensitivity: Adjustable ::}/://}\ 2(1 - SO, 30bcams • Almabletodcsireddirection with2balljoints ·-?{(/i\i • Switching Capability: 500W max. incandescent• Operation ) ) ) Modes: OFF, AlITO, TEST, MANUAL, ON. Y s 5350 was $135.00 SPECIAL : roNL y $99.oo SAVE $36.oo Lun un IC STEREO FM $79.00 (3) tor $180 MITIER f: ;I • K 1120 Normally $43.50 32.00 SA VE OVER 25% Now Onl PCB SHORTS LOCATOR AUTOMATIC N1CAD EA June 1989 • Ideal for PCB industry and hobbyist. A small self-contained unit, battery operated. Uses audio tone to locate shorts. Has three sensitivity ranges. User can thus concentrate on positioning of test probes without having to watch a ~ter. Simple to construct and operate. S-iltery A!'! . · t ~'I 2 AA.~. .3 4. f.:.). t!l(lr:')A.n !-i◊::'!:-nAh :-,.:, 6~:m!'I . 5 1 ! Pulse Count 'l)pe Our 1989 model !RD now s 5301 $79 <at> 0 Detector includes pulse count circuitry with a specific time delay between pulse sensing. 1111'cc puli!les of IR radiation arc required to trigger the detector. Features: Lens wide angle & narrow angle I !2Y DC Powered. TRANS- ':~ :; t.tY(L Nl»ft Ideal for checking insulation in transformers, TRANSMITTER appliances, automotive generators and ,- - - - - -- - - ---'l{Sce Silicon chip Oct 88) alternators , house wiring etc. Turn your CD player Into a Mini FM Transmitter Breakdown can be measured at either 500V or Converts ill signal to PM signal so you can tu~ in with lOO0Y depending on the situation. your Walkman or portable radio• Powered by one 1.5V Perfect for work van, toolbox or work bench. penlite battery• Single IC circuit makes it easy to build. K 2555 .... : .:-:-:-:-•-·,· (;) ~ 'MINI MITTER FM STEREO c::: CS. D 10!).nAh ~.2~h C~ut"]~ ; .,'·s():: I '""' r>!l~A ~OmA I ;?.'..>:n.#. , T6~kie <:h:::(tle .., 2:1¾ i K 1650 $38.00 At L1ut! Here i.s a faUJ auto~tic NiCod charger capable of charging just about all of the NiCads available. Ideal for service tcelmieianB and hobbyislll alike. Allows componenlll to be quickly and Features Include: Auto switching to trickle cleanly removed with one hand. Com:::11 with a cleaning wand Ea~ single handed charge, charging state indicators and five action. Simple cleaning action, 240V AC, S0MH1., 30W SEC Approval W/22281 selectable charging times. T 1250 NORMALLY $59.95 YOU SAVE $10.00 Requires only 12 Volt AC power supply. ·•••> >? J?HG>f\J.E<r>•BE>EB [Ol!lltER•EE\~L.TR Q f\J '--~• SQQQ ~990Qi. /./ (I Gel Cell Charger N1CAD (See Silicon C_h lp July '89) All mains Transformers Primaries 240V • Specifications llsted refer to secondary windings. NEW NEW NEW NEW NEW NEW 1111:i month } M 2851 / ' \ M2852 '·?:/:/::/.• M 2853 \ ~ ~~~~ (.·.·. ·•···•·>)•· MM 6672 2156 CT 12.6V CT 12.6V CT 12.6V 30V CT 0, 12, 15,18V at 6,9,12,15Vat 15, 17.5,20,24,27.5,30V at 150mA 300mA 500mA 150mA 1Amp 2Amps 1 Amp :~::! :::~~ FROM $1 .99 CaLNo. S 5020 AA 1 .2V Normally This Month $ 3.99ea $2.99ea 500mAh 10 up $ 3.25ea $2.SOea 25or more $1.99ea S 5021 AAA 1 .2V 180mAH $ 4.SOea $ 3.75ea $3.95ea 10 up $3.25ea MICROEYE VE CTQR $23.50 $$8 . 95 $$8 ._ 4 5 The intelligent way to charge Gel Cells and sealed 5 95 6 50 lead acid batteries• Monitored battery voltage $12.50 $11 .50 statcschargingcunent•Canaddyoarstobattcry The First Detector with $17.95 $16.50 life• Microprocessor controlled• Ideal forradio G A Di d $16.50 ,.....;$ ! .l!.:5:'.,:·~ 00 ~ !::::am:a:tc:ur:•:and=m=odo=lra:c:in:-g-::car _,,-i-Jd/ii]; r veccr s:::::===: Until now GaAsadiodes S haveOonly eS been used in HEADPHONES SUPER PRICE Why pay $400 or more tor a David Clark set? sophisticated military radar equipment. The Microcye Vector is the first consumer electronics product equipped with this new technology. Why GaAs diodes make the difference • Lower threshold allows for a better signal to noise ratio • Lower signal conversion loss • Low ON EA 8 Higher barrier reduc.cs noise. Quite simply GaAs diodes increase the sensitivity of the Microeye Vector. • Simply plugs into your cigarette lighter socket or can be direct wired into your existing car wiring• Clips onto visor• Detects SECTOR BURGLAR AVIATORS HEADSET WITH OIL FILLED EAR CUSHIONS ALARM KIT mobile radar equipment• Highway/City/Modes • Separate audio alerts for X and K bands • Visor bracket• Velcro • Cigarette lighter ~--.. • High performance, noise attenuating earphones. • Noise cancelling microphone • Cushioned head pad • Super sturdy • Gn:at performance • Superb, professional pilot's headset will last a lifetime with reasonable treatment. • Includes standard aircraft jacks. Now available from Altronics Dealers K 1685 SENSATION I Protect your Home or Business from Intruders with this "State of the Art" Burglar Alarm System and save $$$ on the cost of commerclal equivalents. Features: • Alann has 8 separate input circuits - 8 sectors can be monitored independently • Each input circuit is provided with an indicator LED and a sector ON/OFF switch. • Individual :,ector isolation allows the user to be in some areas of the premises while others remain protected. eg Inside OFF, Ou.side ON.• Inputs accept both normally dosed and normally open sensors. • Two inputs provided with an entry delay (between 10-7S seconds). • Internal trip warning buzzer - alerts o~r/occupant of pending alann operation - great for the "forgetful" amongst us. This buzzer is presettable between 5 and S5 seconds prior to alann. • Unique circuit detects automatically when either N/O or N/C loops arc either open circuit or dead short, eg someone Is trying to bridge reed switches etc.• Switched output can be used to send a silent alann through an auto-dialler circuit or similar. (See EA Jan/Feb'85 or our 1989 Catalogue for full features) Kit (Less Battery Back Up) C9010 0 N L Y Back Up Battery 12V 1.2AHS 5065 K 1900 $169.00 149.50 plug. Microprocessor Controlled Detector Clips on to Sunvisor Invisible from outside your vehicle - this fantastic high spec. Radar Detector detects X and K Band Radar up to an amazing 13kM. A 1530 Normally $499 Save $100 this month $29.95 ...... > ally exciting news is that all of peakers are available at such 11 ount price for this month • but be uick - 11tocks are limited. 15" (375mm) WOOFER Ultra High Power Capacity rI sA"~ •> NOW .1 >< Polypropylene Bass Drivers t.•••• f Our ALL NEW "Black" polyprop cone Bass Drivers exhibit qune astonishing low register reproduction . Power ratings quoted are conservative. Not the cheapest but definitely the BEST VALUE we know of· ANYWHERE. 12" (300mm ) WOOFER Huge 120 Watts RMS Massive 200 W Max. C3075 C3070 Normally $129 Normally $99 NOWONLY$99 YOU SAVE $30 NOWONLY$89 100watt RMS 150W Max. HUGE SAVINGS ON SPEAKERS 8"WOOFER 60Watt RMS 100W Max. c 3060 Was $49.95 Now $39.95 SA VE $10.00 •f' · -.. 61 /2" WOOFER/Midrange 30Watt RMS SOW Max. C 3055 WAS $29.95 NOW ONLY $24.00 ~ 10"WOOFER ,, 60Watt RMS 100W Max. C3065 Was$69.00 NOWONLY $49.00 61 /2" Mid Range 30Watt RMS SOW Max. with sealed frame Was $27 .50 NOWYOU SAVE AT$22.00 c 304s Design Quality Weather Proof Speakers and Sound Columns by Redford • Rugged extruded aluminium construction • superb powdercoat industrial paint finish • Engineered in Australia• Excellent reproduction • Superior to imports - yet a fraction of the price! Great for the back patio, swimming pool, games room, den, pool room etc. Wide Range Weather Proof Extension Speakers for Your Stereo System Redford is the soluticm for high quality sound reproduction outdoors. the five models to choose from "fill the bill" from aplications on boats to high grade paging and music entertainment installations. RUGGED EXTRUDED CONSTRUCTION These vibration free enclosures are constructed from die extruded heavy gauge aluminium and finished with inacdibly durable industrial powderooat enamel. The speaker ends are sealed with gaskets and tough moulded ''LURAN S" UV resistant end caps. The end result is "good looks" together with assured rugged durability for the Australian environment. EXCELLENT REPRODUCTION The drivers have bocn chosen for wide range, low distortion, mid•range "presence" (essential for high grade vocal work) and high efficiency in general. Power Capacity: for short term the drivers will safely handle 150% of rated power. acoustic wadding is used to dampen bass resonance. Weather Proof Construction and use of "Doped Cones" foam plastic and cloth is sandwiched between baffle and front grill to .prevent water ingress. A first for Redford is the use of a patented cone moisture repellant process proc.css for all mcx:fels. SouND CoLUMN TO M1c. STAND ADAPTER Ideal for portable PA systems. Adapter simply screws into colwnn speaker and on to standard 5/8" 27TPI microphone thread. Suits all speakers/sound colurrms. Suitable for use on C 0505, C 0510 type microphone stands. 'A' 250x165x120mm C099o $9.95 STYLE CAT NO A C 0932 C 0934 C0938 C0940 C 0941 SPKR SPKR SPKR SPKR SPKR DESCRIPTION CLM W/P 15W/4 OHM WHT CLM W/P 15W/4 OHM BLK CLM W/P 10W/16 OHM WHT CLM W/P 10W/16 OHM BLK CLM W/P 10W/100V BLK CLM W/P 10W/100V WHT CLM W/P 20W/8 OHM BLK 20W/8 OHM WHT EACH PER PAIR 99.00 190.00 99.00 190.00 99.00 190.00 99.00 190.00 240.00 125.00 125.00 240.00 280.00 149.00 280.00 149.00 4LTilOnlC) 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A.6000 ALTRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. Pie•• Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forget our Exprna Mall and Phone Order Service· for the coat of a local call, Bankcard, Yiu or M•terc:■ rd holder• can phone order for ume day dnp■ tch. STYLE CAT NO C0945 C C C0946 C C0950 C0955 C B C0970 SPKR SPKR SPKR SPKR SPKR DESCRIPTION CLM W/P 20W/100V BLK CLM W/P 20W/100V WHT CLM W/P 40W/100V BLK CLM W/P 40W/100V WHT CLM VIFA 100W/8 OHM BLK CLM VIFA 100W/8 OHM WHT CLM VIFA 40W/100V BLK VIFA 40W/100V WHT EACH PER PAIR 179.00 330.00 179.00 330.00 245.00 450.00 245.00 450.00 199.50 390.00 199.00 390.00 225.00 430.00 225.00 MORE AL TRONICS DEALERS WANTED If you have a Retail Shop, you coul~ increase your inco~e significantly by becoming an Altronics Dealer, Phone Chns Campbell (09) 328 2199 for Details. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 9 days from day you post order to when you receive goods OVERNIGHT JETSERVICE Upto3 Kg is$8.00-3Kgto5Kg is$20.00-Weprocess your order the day received and despatch via. Overnight JelHrvlce Courier for delivery next day Country areas please allow additional 24-48 hours. 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COUNTRY ALBANY BP Electronics ■ 412681 ESPER.,t.NCE Esperance Communications 713344 GERALDTC,tl K.B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521500 Farmer Electronics 522388 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 6241331 VICTORIA CITY All Electronic Components 6623506 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN CAPALABAKingsway Electronics 3902399 WOODRIDGE David Hall Electronics8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724459 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 7724466 SA CITY Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 COUNTRY COFFS HARBOUR Coifs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WA 1st April, 197Australia. Colin, mate: You've heard the phrase "always to quit that was the problem. One a bridesmaid, never a bride". I now night, he'd been at some do for the understand what it means. new police commissioner. They'd When I wrote last, I was anmet when Peter went to do a quote ticipating some good fortune. Infor a security system in the copstead, what I write now is no brag, per's house. Seems some villain had just fact. I'd been doing a fair bit of broken in and stolen the man's the manager's job before he resigndress uniform. ed and thought I'd be promoted. Anyhow, about 3 o'clock in the Instead, the state manager said morning, Peter was driving round ._._t.,...,.,,ey, ~4.ting on.me tB,£JORtiaue -and reun&6 amelo etr . 'Yo rota hold the department together unbably know it - the circular street til they could get a new manager. I near the restored colonial area. expressed my interest in advancePeter had entered from a side lane ment. The boss, however, said that started going around and was to~ the head office was sending a real fogged to stop. A constable pulled expert to repair the damage that him over and Peter abused the poor Peter had done. lad; told him he'd report him to I was going to say that Peter had Commissioner Bloggs whom he'd a drinking problem but that's just left a party for. wrong. Peter had no problem with Peter sure had luck. If I tried his drinking; it was knowing when that, I'd still be in jail! But he had By RICHARD KOPF 82 SILICON CHIP contacts and reputation, too. One tlay he went to lunch with some of his mates and got home about dawn the following morning. When he came in at 9:30, he got a cup of coffee, then didn't drink it. He came to me and said, "c'mon, we got to go do a quote". He told the office manageress we'd be out for a couple of hours. In the car, he asked, "where's the best place to drink this early in the day?" The expert Well, the head office expert owed up, a tubby little Welshman, about 26. It was obviously " jobs for the boys" time, for this callow youth had never worked in the security industry before. That didn't stop him from telling me that what I was doing and how I did it was all wrong. I was still struggling over that bank job. Which bank? Doesn't matter ... The building services manager there was always on my back to fix the problems that our management had created. He understood the source of the difficulty and also knew I'd do my best to sort out the mess. A real problem existed where responsibility for a sub-system was vested in more than one company. For instance, we had the security monitoring of the site. The front door tied into our system from the card access panel which was in- ~ WI-\E:.N 1: ARRIV~, I 1 WA'S NO,- HARD , 0 se..e: -rHA-r 1"\-\e:. ~N\f>E:.'R ~t>s ,N ,He. oooR. CONTROLPANE:-l..- HA'D c:AUSe::t> '11-\€ T'R.OU~E: o .... stalled and maintained by our arch rival. One night, a city copper sauntered past and was aghast to see the door wide open. Calling for backup, he crept inside and ultimately surprised a bank guard making his internal rounds. After recovering from their mutual fright, they both inspected the premises, finding nothing else amiss. The chief security man was called. He threw a wobbly and called the outside security companies' managers who then passed the buck down the line. I was alerted to go immediately to the site - it was about 4am. When I arrived, it was not hard to see that the jumper leads in the door control panel had caused the problem. One of the opposition's apprentices had been doing some system maintenance the previous day. He had forgotten about the bypass. I didn't blow the whistle on them, however, but gave a convoluted explanation to the building services manager about a discovered incompatibility between our two systems. It was even sort of true. The same pulse that caused the door to open kept an open door alarm from going to our control centre. Yes, but the jumper leads didn't help matters. New job The upshot of this situation was an offer from the opposition's state manager to come work for them. That bloke was keen to get back to his home town and dangled the promise that I would take over when he left. Giving notice was no problem. The Welshman was really taken aback though: "Have you not been happy here, then?" In my final week, the bank's building services manager admonished me that the front door was my company's responsibility and perforce mine to finish before I left. The last day was really a joke. The Welshman sent me back to the bank. I spent most of the day in the control centre swapping jokes with the guards. After lunch, I called the office and asked the state manager when I would get my separation pay. He said he'd send the Welshman down with it. At about 6pm the bloke arrived, shoved an envelope at me, turned and left. That was it - no fanfare, no farewell from the other staff I'd worked with. On Monday morning, I went to my new job but it was the same old drive. Funny that the two rivals faced one another on the same street. Back to the bank My new boss decided I'd be called a technical sales representative for the time being. On Tuesday, he told me to go see the building services manager at that bank. JANUARY 1990 83 THE TECHNOLOGY LETTERS - CTD On arrival, BSM said, "What are you doing about the front door situation?" "But when I worked for A", I protested, "you said it was their responsibility - and mine as their employee. Let the Welshman fix it". "You're the only one that understands the problem". I reluctantly agreed to let my manager make the final decision. He thought my sorting out of the mess was a fine idea. So I did not get rid of the ~lbatross after all. My new "boss explained his reasoning: "You're the technical bloke. I'm only administrative". The next day, it must have looked unusual to see me in a 3-piece suit with a meter and tools - and a stepladder working on that blasted door. Inside knowledge I had one advantage in my new position, in that I knew both companies' equipment. Thus, when I quoted a job, I had a fair idea what the opposition would be doing. More often than not, I was able to undercut them. Too bad I was on fixed salary, rather than a base plus commission. There was an implicit understanding in government tenders that certain jobs would go to certain companies. Mind you, I'm not saying there was any wrongdoing just an attitude about sharing the work out in the private sector. Very often, I was able to win a tender that would have been theirs by interpreting the specifications wisely. It gave me a great deal of satisfaction, if no extra money. I inherited another project straight away, for a private printing outfit which had won a contract to do certain government printing jobs. One of the provisos was that they install a complex internal security system. Immediately, I perceived one problem. Ordinary vidicon cameras had been quoted for low-light situations. I went to their services manager and tried to get this changed but they could not afford to do it right. 84 SILICON CHIP When the cameras were commissioned, their guards complained immediately that they were useless. My boss demanded that I do something about it. "Can't you open up the lens", he whined. I tried to explain that the outside camera by the loading dock was susceptible to sunlight. If I irised wide to get an acceptable picture from the night-time lights, the tube would get a burn during the day. "I thought you were such an expert on this video stuff'', he sneered. "As you've pointed out, I've got the technical background. You're administrative and cannot change the laws of physics. If you expect me to, better order a magic wand". Bossie stormed off in high dudgeon, accusing me of not cooperating. Several hours later, he returned and ordered me to set the camera up so that the evening guard was satisfied. Two days later, they called to say that the camera was not giving good results. In the end, we replaced the burnt camera at our expense with another unit fitted with an auto-iris lens. "That cost us a packet", my glorious leader said. "I don't understand with your experience how you could allow such a thing to happen". The next fiasco The next fiasco I unwittingly let myself into involved film cameras. I walked into the technicians' workshop one morning to discover one of the blokes loading the cassettes with bulk film. "Third time that's happened this morning", he moaned. "You could put a sign on the door". "I never thought of that ... " Taking a look around the room with the light off again, I noted more than a few light leaks from outside. Guess a little fogging didn't really matter, once I discovered how the cameras were set up. These were 35mm motor drive units, tied into the security system. Once again, they had fixed lenses. Set-up was no problem for a technician though - just point it approximately in the right direction and set it for f/8. Just then, the boss wandered in. "I've been meaning to ask if you know anything about film processing". I conceded that I had done some work in this area and found that they had been sending the cassettes after changeover to the head office. Now the contract called for test prints to be given to each branch every three months. Some places had not had a decent print for well over a year. For the next two or three weeks, I went around to various banks, assessing performance. About a third of the units did not function at all. The ones that did work could not produce a decent picture because of inadequate lighting. The film stock they were using was not to spec. It was a cheap and nasty industrial grade with grain the size of golf balls. About that time, we were called out one morning to a suburban branch where a robbery had taken place. Our tech removed the cassette and gave it to the police for processing - required procedure, you see. No useful prints came out of it. Apparently the reel had jammed in the transport some weeks before. "I'd forgotten about that", the branch manager admitted. This poor chap was surely unlucky. He'd been robbed before, in a country branch in the north of the state. And one time, he'd been delivering a satchel of money to the head office, stopped for a counter lunch and returned to the car to discover someone had broken in and taken the bag of loot. I set up a processing system and got all the test prints up to scratch. Doing it in-house saved our company heaps and satisfied the customer at the same time. 'Tm a little put out", my boss said by way of thanks, "that I'm having to do quotes you should be doing". As it happened, I did not have to put up with this sort of thing much longer. We got the word that my .DON'T" BE: F'RIGHTE:.NE.D ·MA'AIV\"'-' YOUR. i:,,.LAR!Y'I TE:LL-S LIS TI-IAT ?ROWLE-R.'S ST"ll-LIV\OVING A'R0UNO 'RIG-H-r a_lN n-llS VE:'R'( ROOIV'\ _, 1/1 JJ) r;. ~ .-- /) 0; - I\ ~ ·._ -~ V - I ---_....._ .. <o~ ~ -ADDING OF F\ N\OT\0 PETE.C.TO'R 10 "tr\E ~- . B.ED'R.00 IV\., ... aspect of it but you surely remember the co-channel interference? That came about because the consulting engineers planned on a 6-channel microwave link system. Phase One put in channels one, three and five. Phase Two, a couple of years later, added two, four and six. Now, the key was vertical polarisation for the first lot and horizontal for the second. But the two year gap and the usual insufficient documentation meant that the second lot of gear supplied was also vertically polarised. Thus the sideband energy overlapped. Acceptance tests, I hear you ask? They fudged them by checking one channel at a time, then took the money and ran. Consultants! I don't know how many people were asked how to solve the problem. Another case of "do it right or do it over". Only it never got solved, since the administration didn't want to spend the money to do it over. Weird designers boss was being transferred. No, he didn't get to go back home. They moved him to yet another state and then sacked him. Last I heard, he was driving a bus. Guess who? I did not get the promotion I'd been anticipating. Instead, the new state manager turned up: Peter the Dipso. At that point, I decided 'to say goodbye to the security industry. In my final fortnight, I knew I'd made the right decision for Peter topped all his other deeds. He was quoting a system for an old maiden lady who was worried about burglars. "Suppose someone breaks into my bedroom some night?", she wanted to know. "Oh that's easy, Ma'am. We'll just add a motion detector in there". The old dear never picked up the flaw in this approach and signed the quotation happily. One more incident: Peter quoted an electronic access system for an armoured car company. When he received the go-ahead, he said: "Hell, we won that job - I was only going through the motions". "Well, you can't lose them all", I quipped. The problem was, though, head office had not yet designed the system. They'd only been working on it for two years and it still had bugs. So, over the weekend, I cobbled together a panel using a Motorola D3 board and sold it on sub-contract. Since the building system had 24-hour power, I never anticipated any hassle and had both the program and ID look-up table in RAM. Every now and again, the data would get corrupted and I'd have to go in - on a service fee - and reprogram it. Not one of my better designs, but a money-maker, what? I've been thinking about construction phases since that bank situation - and remembered our sojourn in the South Pacific. I don't think you ever got involved with this Where do these weird designers come from? Newness in the field can excuse some things but how do you explain a bloke with 15 years' experience making a really basic blunder? That TV station I worked at before had a new building, with all the bells and whistles. The architect had specialised in broadcast facilities. Why then did the sunlight from the foyer reflect off the colour monitors in master control? The village idiot would have picked up that flaw from the plan. But not the chief engineer, station manager, or owner. Once the building was finished and the truth had reared its ugly head, the glass control centre was masked off from the outside world with heavy drapes. TV is heavily on my mind, since I've been offered a job at a country station, interstate. The family is a bit reluctant to move but I feel it's time for a change. Hoping to hear from you soon. Best wishes, Richard. ~ JANUARY 1990 85 PT.27: A LOOK AT VERY FAST TRAINS THE EVOLUTION OF ELECTRIC RAILWAYS The very cutting edge of railway technology lies in futuristic Very Fast Trains running at 350km/h and more. This month we look at the idea's origins, some way-out ideas from around the world and real engineering development in Europe, England and Sweden. By BRYAN MAHER The concept of very fast trains competing on equal footing with passenger jet aircraft is not new. But today the idea has moved from the realms of fantasy into the real world of nuts, bolts, motors and welded steel. We have not yet reached a limit to the speed that wheel driven trains can achieve. By commercial jet, the SydneyMelbourne flying time is 1 hour and 15 minutes for the 700km route, giving an average speed of about 560km/h. True we do not yet have BRITISH RAIL HAS INTRODUCED these VHS (very high speed) trains, pulled by its class 91 locomotives. The locomotives run at speeds up to 240km/h, pulling five tilt-body coaches. 86 SILICON CHIP trains travelling anywhere near that speed but do not think that it is an impossible goal. Since the dawn of railways, researchers and experimenters have toyed with schemes aimed at very high speed rail travel. Many ideas proved impractical but a few very advanced radical inventions are still being pursued. Early linear motors Experiments with high speed rail vehicles have been going on for years. A report from England in the 1950s described how a 4-wheel test truck ran at speeds of 1600km/h on a track a few kilometres long. It had steel rails embedded in concrete TIDS EXPERIMENTAL MAGNETIC levitation train produced by Krauss Maffei in Germany used a linear motor buried in the track for propulsion at quite high speeds. Magnetic levitiation and linear motors are wasteful of energy though and present big problems when it comes to track switching. I and buried in the concrete between the rails were the winding and iron cores of a linear motor. The truck was extremely low, at less than 200mm high, resulting in little air drag. Stopping at the end of the straight track, according to the report, was simple: the truck shot off the track into a large lake! That fascinating little system was not designed with rail travel in mind but was intended to tow heavily laden aircraft up to about 400km/h, to assist take-off. Readers who doubt the ability of a motor to attain such speeds should consider the peripheral speed of a 60Hz, 2-pole synchronous motor which will have an operating speed of 3600 RPM. If the rotor is one metre in diameter, the rotor circumference will run at 678.6km/h. If run at a higher frequency, it would travel even faster. Clearly, a linear motor propulsion system for a train could achieve very high speeds. Wheel-rail problems Do trains actually need steel wheels running on steel rails? This arrangement does give minimum rolling friction but steel wheels cause noise and vibration. Pneumatic tyred trains running on steel tracks have been tried (eg, our monorails and some French suburbans). Experience shows a decrease in noise and vibration at low speeds but such tyres are a failure at high speeds. But does the train need to contact the track at all? Could not the train float above the rails as it speeds along? Yes, in principle this can be done. Fig.2 indicates the idea which is called RUNNING WHEELS LINEAR -MOTION magnetic levitation or maglev. That's nice, but how do you propel it? Three methods have been tried: • Engine driven propellor (as in hovercraft); • Horizontal jet engines; • Electric linear motors. Magnetic levitation Magnetic levitation has been combined with linear electric motors in experimental trains on a limited scale in England and Europe. This system has wheels for emergencies only, the train normalSTRAIGHTENED OUT ROTOR MAKES STRAIGHT LINE MOVING PART GROUND 3-PHASE SUPPLY 3-PHASE STATOR COILS FIG.1: A LINEAR MOTOR IS SIMILAR in principle to the rotor and stator windings of a conventional induction motor laid out flat. The locomotive windings induce currents in the stationary windings under the track and the reaction between the magnetic fields provides propulsion. JANUARY 1990 87 MAG-LEV TRAIN PASSENGER COMPARMENT IR HEIGHT SENSORS FIG.2: THIS IS THE GENERAL ARRANGEMENT of coils for a maglev train. Close control must be maintained over the elevation and transverse alignment of the vehicle. ly floating a few centimetres above a special track, suspended vertically by magnetic fields. As Fig.2 indicates, both elevation and alignment magnets are needed but these can be combined in a V-shaped track arrangement. Control systems to maintain constant height above the track and correct transverse alignment are mandatory. Train sensors continuously measure elevation and side clearances, feeding data to the control electronics. Some designs have used lifting/repulsion magnets, others have tried magnets above and below the rails. Experimental maglev trains were built in Japan, England and Germany and the latter country proved that B00km/hr is possible, at least over a short distance. In Munich, the Krauss Maffei organisation built the Transrapid-04 Maglev test vehicle and track for further research. Also in Germany a twosection maglev train was designed to carry 96 passengers at 400km/h. In these maglevs, magnets provide the lift as well as both traction and braking forces. In the USA, the Department of Transportation sponsored the Grumman company in building a jet propelled vehicle and special 88 SILCON CHIP track. However, this may be classed as a guided hovercraft rather than a train. British Rail Research, always interested in faster and better railways, espoused a maglev train system between Birmingham National Exhibition and the airport. The tolerance achieved in elevation above rail and transverse alignment was ± 13mm. Fantastic! But that installation did point to the probable future role of maglevs; in short, fast, comfortable shuttle services in crowded cities. Magnetic field problems Still, the world's railways have not rushed to install maglevs on useful long distance trains. The advantages of a smooth ride free of the imperfections of wheels, rails and the variable contact forces between them may be attractive but the strong switched magnetic fields produce problems. The magnetic fields are not completely confined to the motor-track space (the ideal aim). Rather, strong leakage fields can pervade the whole carriage. And because the magnetic fields are switched, they could induce currents in anything conductive within the passenger compartments. This means that harmful stray currents could flow in all structural metal and in the electronic control and communication circuits. Harmful currents could pass through the passengers too, particularly if they have heart pacemakers! And in today 's energy conscious world, maglevs appear to have a further disadvantage because they are very wasteful of energy. As well as the power needed for acceleration and traction, maglevs consume large amounts of electricity in the lifting magnets. Future superconducting magnet coils could overcome this problem. Another problem: how do you change tracks when the train is virtually captured between those magnetic guide rails? This is a worse problem than that described in the episode on monorails! Conventional trains With these problems unlikely to be overcome in the foreseeable future, it seems likely that steel wheels on steel rails will be with us for a long time yet. So how do we increase the running speed? Many factors help to slow down locomotives and trains: • Sharp curves on existing rail corridors; • Steep hills; • Underpowered locomotives; • Insufficient ballast around sleepers, causing spongy track; • Rails too light; • Bogie suspension systems inadequate at high speeds; • Too much unsprung weight in bogies; • Bearing resistance in bogies; • High drag coefficient, leading to air turbulence at high speeds; • Air drag and flying effect of pantographs in electric locos; • Inadequate braking at very high speeds where wheel-rail grip is reduced. Sharp curves Sharp curves are the most serious problem for very fast trains. In fact, they are worse than heavy grades. The density of built up areas in England and parts of Europe (particularly Switzerland with so much mountain country) will not allow WHILE SELF-STEERING BOGIES can negotiate track curves at very high speeds, the passengers object to being thrown from side to side. If track curves cannot be straightened, the solution is to automatically tilt the coach bodies while not moving the centre of gravity. This system, devised by ASEA/ABB, keeps wheel loading constant. new straighter tracks to be built. This has prompted years of research into tilt-body passenger carriages. the floor automatically moves to the right. The aim is to keep the car wholly within the loading gauge. Tilt bodies The speed of a train ascending a steep grade depends directly on the power-to-weight ratio of the train and the running speed at the foot of the hill. Steep grades up to 3. 5 % would be no problem to a very fast train (VFT) if the train had sufficient power-to-weight ratio and there were no sharp curves. Therefore, for speeds above 300km/h any VFT track must be a dedicated new route to allow an almost straight run approaching and ascending hills. Tilt-body passenger coaches are designed to negotiate existing curves above the present speed limits which are set to stop passengers from being thrown from side to side. Bogies, especially the selfsteering type, can be designed to ride at surprisingly high speeds around curves, the limiting factor being the comfort of passengers. To be successful , hydraulic tilting of the coach body must be automatically controlled to suit the speed and track curvature. However, the tilted coach must not move outside the track loading gauge, otherwise it may swipe trackside structures. England and Sweden produced prototype tilting trains but the implementation is not easy. ASEA of Sweden (now ABB) has designed an improved method so that when the top of the car tilts left, for example, Steep grades Rail and ballast For fast travel in safety the track must be exceedingly strong. This means very heavy rail, with 68kg/m rail the top choice. The ballast should extend at least 300mm below and as far out as practicable on each side of the track to prevent sideways movement of the sleepers. Though many modern railways opt for reinforced concrete sleep- ONE OF THE SECRETS OF really high speed running is to use locomotive bogies with low unsprung weight. These bogies, used in the British Rail class 91 locos, have the motors and disc brakes suspended from the loco body rather then being supported directly on the axles. JANUARY 1990 89 ANOTHER COACH TILTING SYSTEM is Talgo, devised by the Italians. The coaches run on shared bogies and are suspended from the top and so are free to swing out on curves. This has the advantage that it is a completely passive system. The drawbacks of Talgo are that the coaches can swing outside the "loading gauge" and therefore may sideswipe trackside structures such as stanchions and signal masts. Wheel and track loading on curves is also uneven. ers, some engineers prefer formed steel units, such as those made by BHP. Steel may be superior to concrete in areas subject to heavy frosts followed by sunny days. Under such conditions the wide temperature changes can possibly initiate hairline cracks in concrete, leading to loosening of rail ties. These effects have been reported in parts of the USA. Bogie suspension The bogie suspension should keep the wheels in contact with the rail at all times. That's not a joke it's a real problem at very high speed. More than this, the suspension must minimise any change in weight-per-wheel during acceleration, braking or traversing of curves. Something as close as possible to independent wheel suspension is the aim, while retaining the solid wheel-axle set. For very high speeds, special wheel flange contours are needed to inhibit bogie oscillation when travelling on straight track. The unsprung weight per axle must also 90 SILICON CHIP be a minimum. This is a major problem in motor driven wheels where the classic axle-hung traction motor and axle mounted gear can more than double the weight of a pair of wheels and axle. High unsprung weight results in less than optimum track adhesion and reduced ride quality for passengers. Ideally, unsprung wheelset mass should preferably be below 2 tonnes for high speeds, with a loading of 18 or 19 tonnes per axle. English VHS The new British Rail VHS (Very High Speed) trains were launched on 11 th August, 1989 on the Intercity East Coast main line run from London to Leeds. These VHS trains consist of nine coaches hauled by one 4.7MW (6300hp) Class 91 Bo-Bo electric locomotive. The loco is powered by four 1.2MW DC traction motors, each 6-pole, fully compensated and separately excited. With a wheelset mass of 1. 7 tonnes, the total (unsprung + sprung) weight per axle is light, at just 20 tonnes. Motor mounting To minimise the unsprung weight, the traction motors and brake discs are mounted in the loco body but they hang down within the bogie frame. Traction/braking drive is transmitted via a rightangle gearbox, a sprung quill drive cardan shaft and flexible couplings. This allows the bogie to move relative to the body while the motors continue driving or braking. The 25kV AC overhead supply is fed via a single pantograph to the underslung main transformer. Secondary windings feed the DC traction motors after rectification. Speed, traction power and electric braking are all microprocessor controlled via an asymmetric oil-cooled multiple GTO thyristor bridge. The electric braking is regenerative, with power returned to the 25kV AC overhead catenary and thence to the national grid system. This is the most efficient method of braking and does not uselessly waste energy in resistor heat banks in the locomotive. To enable braking at all times, the traction motor field coils must be excited. To provide this function in the 91 class loco, the field converter uses GTO thyristors with power supplied from batteries . The coaches are a new tilting design. At the rear, a DVT (Driving Van Trailer) is fitted with a driver's compartment. This rear driver's console, with full control of all loco functions and braking, is used when running in the reverse direction. Double ended operation saves considerable turnaround time at terminals. The design principles for this train, as regards vehicle ride quality, track-following and stability, were derived from research previously done on the now aborted British Rail APT (Advanced Passenger Train). 91 Class results The 91 Class locomotives are rated at 240km/h maximum speed with a dynamic electric braking range from 225km/h down to 45km/h. The complete loco weighs 80t and is designed to haul 520t trains on the east coast route by day, or 750t trains on the night run. Most day journeys on the east coast will involve long continuous runs at a steady 225km/h. On the west coast, the more curved route will limit speeds to 200km/h. On both east and west coasts, sleeping car trains will have a top speed of 160km/h. Swedish tilt-coaches Though the first trains using automatic body-tilt ran in Canada, on the UAC Turbo trains, Europe has taken the lead. SJ in Sweden contracted with ASEA in the design and supply of a test high speed train to run on existing tracks but to cut 25% off run time. The design being tested consists of five stainless steel tilt-body cars hauled by an electric locomotive. The last car is also a driving trailer with a driver's console for use on the return trip. The coach body tilts about its own centre of gravity so that no change in wheel-track forces occur. Tilt is limited to ± 6.5° but even so, this allows the ANTRIM TOROIDAL TRANSFORMERS coaches to negotiate curves at speeds 30% faster than non-tilt coaches. Tilt control is initiated by an inertial captured gyroscopic transverse force transducer. This automatically takes account of curve radius, train speed and track superelevation. Should the train stop on a curve the coach automatically returns to vertical position. The tilting coach bogies have self-steering axles to allow operation up to 200km/h on existing tracks with almost negligible flange wear. Next month we will continue this discussion, looking into some high speed trains which are regularly scheduled for speeds above 300km/h. ~ Our thanks to Lars Persson, ABB, SJ, CFF, GEC, Malcolm Parsons, BR, John Nicolson, VFT Australia, Krauss-Maffei and DB of West Germany for data, photos and permission to publish. General Construction OUTER INSULATION OUTER W INDING W INDING QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PRICES. INSULATION INN ER W INDI NG - - ; _f-i+ TAX PAID PRICES 15VA 30VA 50VA SOVA 120VA 160VA 225VA 300VA 500VA 625VA 1- 9 10+ 32 .80 31.70 36.00 35.00 37.20 38.50 41.75 40 .35 44.95 43 .50 55.70 52.20 62.00 58.20 72.80 68.25 100.00 93.75 112.00 105.00 Enquiries from resellers and OEMs welcome. Quantity prices and data sheets available on request. Distributed in Australia by Harbuch Electronics Pty Ltd, 90 George St., HORNSBY, NSW, 2077 Phone (02)476-5854 Fax (02)476-3231 JANUARY 1990 91 OSCILLOSCOPES SPEAKERS BOXES TEST EQUIPMENT LOGIC PROBE (LP-2800) ROYEL SOLDERING STATION • Useful for TTL or CMOS has high and low indicator leds and also with pulse memory. • This is a very handy tool for the hobbyist or serious technician for tracing those hard to find faults on logic boards. The all solid-state heat sensor and control unit allows the selection of the appropriate soldering tip Idling temperature. The very high-powered element (relative to the size of the tool) will replenish heat drained from the tip during each soldering operation and will recover the tip tempreture moments after the tip is lifted. • Zero voltage switching • Zero tip potential • Aux ground connection • For soldering ironsCT6 (3mm Tip), CT7 (5mm Tip) 011272 .................. $34.95 LOGIC PULSER (LP-540H) 20MHZ DUAL TRACE OSCILLOSCOPE CRT DISPLAY • 150mm rectangular VERTICAL DEFLECTION • Deflection Factor: 5mV to 20VI Dlv on 12 ranges in 1-2-5 step with fi ne control • Bandwidth DC: DC lo 20MHz (-3d 8 ) AC: 10Hz to 20MHz (-3d B) • Operating Modes: CH-A, CH-B, DUAL and ADD (ALT/CHOP L202 only) • Chop Frequency: 200KHz Approx. • Channel Separation: Better than 60d B al 1KHz • Can be used directly to inject a signal into logic circuits without removing IC • Compatible with TTL, DTL, RTL HTL, MOS and CMOS SERIES4000 SPEAKER BOXES 01 1274 .................. $42.95 FOR AN AMAZING ............$250 GENERAL TOOLS TIME BASE • Type: Automatic and normal triggered in automatic mode, sweep is obtained without input signal I BATTERIES • Sweep Time : 0.2µ Sec to 0.5 Seel Div on 20 ranges in 1-2-5 step wit h fine cont rol and X-Y • Magnifier: X5 at all ranges TRIGGERING • Sensitivity In!: 1 Div or more Ext: 1Vp-p or more • Source: INT, CH-B, LINE or EXT • Triggering Level : Positive and Negative, continuously variable level; Pull for Auto • Sync: AC, HF Rej, TV (each+ or -) at TV Sync. TV-H (line) and TV-V (Frame) sync. are switched automatically by SWEEP TIME/Dlv switch. HORIZONTAL DEFLECTION • Deflection factor: 5mV to 20VI Div o n 12 ranges in 1-2-5 step with fine control • Frequency Response: DC to MHz (-3dB) • Max Input Voltage: 300V DC + AC Peak of 600Vp-p • X-Y Operation: X-Y mode is selected by SWEEP TIME/ Div switch • Intensity Modulation Z Axis: TTL Level (3Vp-p-50V) + bright, - dark OTHER SPECIFICATIONS • Weight : 7Kg Approx • Dimensions : 162(H) x 294(W) x 352(D) mm 0 121 05 .................................................................. $695 MICRO CUTTING PLIERS AA SIZE NICAD Great for detailed cutting. These have a stainless steel head and plastic insulated handles. Length: 90mm T12050 .................... $9.95 Nominal Voltage : 1.2V 450mAH S15020......... 0NLY $1.50 SURGE PROTECTOR MICRO BENT NOSE PLIERS •• THE BUTTON SPIKE PROTECTOR Simply plug the button into an outlet and It will protect all equipment plugged Into adjacent outlets on the same branch circuit. SPECIFICATIONS: Voltage : 240V Nominal Total Energy Rating : 150 joules Response Time: 10ns Protection Level: 350V peak X10087 ..................$39.95 40MHZ READ-OUT OSCILLOSCOPE (B): 0.2µS-0.5mSI Dlv±3% In 1-2-5 steps (X1 only) • Magnified Sweep: 10 times±5%, Max 20ns • Linearity: ±3% or better 0 12107...................................................... .........$1,695 ROD IRVING ELECTRONICS Please quote this advertisement for the prices listed for this month. SYDNEY: 74 Parramatta Rd. Stanmo re 2048 Phone : (02) 519 3134 Fax: (02) 519 3868 MELBOURNE : 48 A'Beckett St Phone : (03) 663 6151 MAIL ORDER& CORRESPONDENCE : P.O . Box 620, CLAYTON 3168 Order Hotline: 008 33 5757 (Toll free , strictly orders only) Inquiries : (03) 543 7877 Telex : AA 151938 Fax: (03) 543 2648 All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE 56 Renver Road, Clayton. Phone: (03) 543 2166 (3 lines) Fax: (03) 543 2648 ORDER HOTLINE 008 33 5757 (TOLL FREE) LOCAL ORDERS & INQUIRES (03) 543 7877 Plastic insulated handles with stainless steel head. Length : 10cm POSTAGE RATES : T12044 .................... $9.95 CLICK SURGE BUSTER It has a long tip angled at 45°, for complicated or delicate work. Stainless steel head with plastic insu lated handles. Length : 10cm 6 PROTECTED POWER OUTLETS Ideal for protecting personal computers, video equipment, colour TVs, amplifiers, tuners, graphic equalisers, CD players etc SPECIFICATIONS: • Electrical rating : 240V AC, 50Hz, 10A • 3 x Metal Oxide Varlstors (MOV) • Maximum clamping Voltage: each MOV: 710 volts at 50 amps • Response lime: Less than 25 Nanoseconds. T12046 .................... $9.95 X10086 ....................$69.95 • Input Impedance: 1Mn:t2%, 25pF±3% • Bandwidth DC: DC to 1MHz (-3dB) AC : 5Hz to 1MHz (-3d B) • Sweep Time (A): 0.2µs-0.5SI Div±3% in 1-2-5 steps (Xl only) f:l:e· STRICTLY ORDERS ONLY HALF ROUND NOSE PLIERS HORIZONTAL AMPLIFIER • Operating Modes: X-Y operati on CH1 -X axis, CH2-Y axis • Sensitivity: 5mV-5VI Div± 3% in 1-2-5 steps TIME BASE • Sweep Method: AUTO, NORM, SINGLE .. -lit.· .. BRISBANE: (V.C.R Computer Services) 64 7 Lutwyche Rd . Lutwyche. Phone : (07) 857 5617 I I T12040 .................... $9.95 VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes: CH1 , CH2, ADD, DUAL, ALT, CHOP • Sensitivity: 5mV-5VI Div 3% in 1-2-5 steps 1mV-1VI Div x5% x5MAG • Bandwidth DC: DC to 40MHz (·3d B) AC : 5Hz to 40MHz (-3dB) • Rise Time: Less than 8.7nS T12570 ..................... $225 NORTHCOTE: 425 High St. Phone: (03) 489 8866 For delicate or high precision electronic work. Stainless steel head with plastic insulated handles. Length: 10cm CRT DISPLAY • 150mm rectangular SOLDERING IRON BENT NOSE PLIERS $1 • $9.99 ......................... $2.00 $10 • $24.99 ..................... $3.00 $25 • $49.99 ..................... $4.00 $50 • $99.99 .....................$5.00 $100 + ..............................$7.50 The above postage rates are for basic postage only. Road Freight, bulky and fragile items will be charged at different rates. Errors and omissions excepted . Prices and specificati ons subject to change . IBM", PC". XT" , AT" , are registered trademarks ol Internation al Business Machines. "Apple is a re gistere d t rademark. Teflon' is a regi ster ed trad emark of Dupont . · oe non 1es reg istered lrademarksoltheir respectiveownars. 4 PORT SERIAL CARD • All ports fitted • Can be used with multi•user systems. X18154 ................ $152.50 512K RAM CARD Ideal for older style P.c·s. Ram is extra. X18014 ....................... $99 1/0 ACCESSORIES • IBM• Colour Graphics Adapter compatible (support 600 x 200 four colour graphics model) • IBM• Monochrome Display Adaptor compatible • Hercules Monochrome Graphics Adaptor Compatible • IBM• Printer Adapter compatible • Support Composite Monochrome monitors GRAPHICS CARD TTL and Hercules compatible with printer port X18003 ....................... $99 ENHANCED GRAPHICS ADAPTOR CARD Auto switch CGA, EGA and Hercules with 256K Video Ram X18070 ..................... $225 • Pocket size, auto-scanning • Allows 2 PCs to share one Printer Serial model : MS•201 • Host•powered VGA CARD Pc•; XT"/ AT• compatible 256K Ram works with OS/2 X18071 ..................... $350 POSTCARD DIAGNOSTIC MODULE Pinpointing component problems in IBM• compatible motherboards can take hours. Usually the whole system has to be working to isolate the troubled area. But not so with the new Postcard Diagnostic Module. So no other cards are necessary to test a bare motherboard. " It now only takes seconds." Simplified debugging for: • Field service• for on•site repairs or maintenance depot work • Manufacturing test· for burn in test flaws and to do quality control • Inspection• Postcard simp· lilies incoming and outgoing test processes on stand X18048 ...................... $849 X19155 .................. $89.95 CL21 COMPUTER LEAD VGA 512K Pc•; XT"/ AT" compatible 512K Ram. Hardware zoom, pan, window. 2 M/BYTE EXTENDED MEMORY RAM CARD X18052 ..................... $225 X18072 ........... .......... $450 • 25 pin D Plug to 25 pin D plug • All pins wired straight through (removable terminals) • Length 1.5metres P19007 .................. $36.95 CENTRONICS CABLE • 36 Way Centronlcs Plug to 36 Way Centronics Plug • Shielded cable • Length: 6 metre P19013 ......... .. ....... $29.95 NETWORK CARD A-NET/ S INTERFACE NETWORK CARD • Fully compatible with SMC, Novell Arenet card • Star•burst topology through RG·62 A/U coaxial cable • Zero wait at 20MHz or higher 80386 machine • 2.5 Mbps transmission rate X18162 ..................... $275 FLOPPY DISK DRIVE CONTROLLER CARD These cards will control up to 2 or 4 double sided 360K IBM• •Compatible disk drives For 2 Disk Drives X18005 .... ................... $52 WITHOUT CABLE Supports 2 asynchronous communication ports. 50 baud to 9600 baud. X18026 ....................... $39 This card will control 2 x double sided, double density drives, and features a serial port, a parallel port, and a joystick port or games port. It also has a clock/calendar generator with battery backup X18040 ....................... $99 SERIAL/ PARALLEL/ GAMES CARD XT•/ AT" compatible 1 parallel port, 2 Serial ports, 2 port games adaptor. X18151 ..................... $115 CLOCK CARD X18024 ....................... $49 X18017 ....................... $29 X18160 ..................... $425 The MIDI DS·401 Card is the PC standard MIDI interface that runs most popular PC music programs for sequencing, recording, composing, music printing, patch editing , music instruction and many other applications. • Run all programs designed for the Roland MPU·401 architecture • Socketed EPROM for easy user replacement • 1/3 length (short) card will fit in any computer accepting standard expansion card, including laptops • Including "Y" cable, external connector box to transport is unnecessary 386SX 16MHz MOTHERBOARD • Processor: 80386SX·16MHz (0/1 wait state) • Co•processor :80387SX· 16 (optional) • CHIPS & TECH NEAT chipsets • (SMT) Surface Mount Technology for chipsets & CPU • Supports up to 2MB on board, (Sixteen 44256 and Eight 41256 sockets) • Three 8 BIT slots • Five 16 BIT slots • Memory Expansion Slot • Optional 2•8MB memory card • Supports LOTUS·INTEL· MICROSOFT (LIM) Expanded Memory Spee. (EMS) version 4.0 • Supports Page Interleave Mode using l00NS DRAM • BIOS: AMI or PHOENIX • Turbo Light and Hardware 4 WAY DISK CONTROLLER • Pc•; XT"/ AT" compatible • 1.44 M/B, 1.2 M/B, 720K, 360K Drives X18006 ......... ... ........ .$129 3.5 M/BYTE EXTENDED/ EXPANDABLE RAM AT* CARD X18056 ..................... $275 1/0 PLUS CARD Provides a serial port, a parallel port and a joystick port, and even a clock/calendar with battery backup! X18045 ..................... $115 GAMES 1/0 CARD Features 2 joystick ports.(DB15) X18019 ....................... $29 AC ADAPTOR • Output: 6V 300mA M19008 ................ $8.95 IBM* CARDS 386 CACHE 25MHz MOTHERBOARD • Processor 80386·25 • Cache controller 82385·20 • Speed : 25 MHz or 20 MHz • Memory : 32KB Cache memory (35ns) • 2 M/Byte RAM fitted (80ns) • 2/8 MB plus 32 bit memory card • Expansion slots: 1 x 32 bit, 5 X 6 bit, 2 X 8 bit • Inter Combo Chip set: 82230, 82231 • BIOS: AMI • Landmark Test: Up to 43.5 MHz • LED display for speed Indication • Ability to run OS/2, MS/DOS, XENIX • Baby AT" size board X18105 .................. $3,000 386 MAIN BOARD • Intel 80386 CPU (20 MHz) • Socket for 80387 Math CO· processor • Power Good Signal on board • Baby size main board • Without Ram • 32 bit Memory BUS system • Built·in speaker. attachment • Battery backup foi CMOS configuration table and real time clock • Keyboard controller and attachment • 7 Channel DMA • 16 Level interrupts • 3 Programmable timers • 8 System expansion 1/0 slots • Including 2 M/Byte RAM X18094 .....................$900 X18107 ..... ............. $1,600 Reset connector • Keyboard or Hardware Reset connector PRINTER CARD • Fully compatible withNovell NE•1000 Ethernet card • Built•in 15 pin D type connector • 10 Mbps transmission rate • Meets the IEEE 802.3 standard MULTI 1/0 & DISK CONTROLLER CARD RS232 (SERIAL .CARD) Parallel interface for Centronics printers. E-NET INTERFACE NETWORK CARD MIDI INTERFACE CARD · DS/401 X18164 ..................... $245 X19150 .................. $79.95 Parellel model: MP·201 Protocol transparent INCREDIBLE G7 MONOCHROME COLOUR CARD X18007 ..................... $139 POCKET AUTO AB SWITCHES I IBM* CARDS NEW PRODUCTS 286 NEAT MOTHERBOARD • Processor: 80286· 12, •16MHz or •20MHz (0/1 wait state) • Co•processor: 80287 (optional) • CHIPS & TECH NEAT chipsets • 1•4MB dual RAM socket • 1•4MB module RAM socket on board • 640KB·384KB memory relocation • Three 8 BIT expansion slots • Five 16 BIT expansion slots • Memory expansion to 8MB • Supports EMS 4.0 • Page Interleave Technology • BIOS: AMI or PHOENIX • Hardware and keyboard switchable Clock Speed • LED speed display • Power Good Signal on board • Baby size main board • 16MHz X18090 ..................... $700 • 20MHz X18092 ..................... $895 • Auto-selection ana autu· transfer between mouse system PC mouse mode and Microsoft serial mouse mode • Microsoft Serial Mouse and Mouse System compatible • Super high tracking speed: 600mm/sec • Super high resolution: 200 DPI (0.12mm/dot) • Silicon rubber coated ball • Optical rotary encoder X19955 .................. $94.95 I PRODUCT SHOWCASE I trigger modes are auto, normal. TVhorizontal, TV-vertical, internal. line and external. The unit is covered by a 2-year warranty. For further information, contact IRH Components, 32 Parramatta Rd, Lidcombe, NSW 2141. Phone (02) 648 5455. Mono graphics card for ATs and 386s 40MHz dual-trace portable CRO Hitachi's new V-422 40MHz CRO is now available from IRH Components. It is a light and compact design with a large 6-inch rectangular internal-graticule CRT with 12kV accelerating potential The list of features includes autofocus and scale illumination, as well as a DC offset function. This allows quick checks of the DC level reading without having to change input coupling ranges. There is also the ability to use alternate magnification which allows simultaneous observation of standard and xlO swept waveforms. The CRO has a vertical sensitivity of lmV/div to lV/div on the x5 magnifier with an accuracy of 3 % and a risetime of 8.8ns. The timebase is from 0.2µs/div to 0.2s/div with a xlO magnifier. The Low-cost field strength meter Looking for a field strength meter to test TV antenna installations? Then look no further. This TC400 Field Strength Meter from Sadelta is designed to measure a wide range of RF levels between 45-300MHz and 470-862MHz. The basic accuracy of the unit is claimed to be ± 2dB on VHF and ± 4dB on UHF. The unit also features the ability to read from 26 to l00dB/µV, and has a builtin loudspeaker, a 0-5000 continuity tester and a sturdy field case. The price of the unit is $699. 94 SILICON CHIP Many high speed PCs are hampered by slow peripheral cards, such as disc controllers and video graphics cards designed to run at the AT standard of 8MHz. This PC-compatible turbo mono graphics card runs reliably on a 16MHz bus and offers an affordable solution for people requiring high quality text and Hercules compatible graphics. The card provides full software switching between half and full graphics mode, allowing CGA cards to run in the system. You can buy your turbo mono graphics card from Electronic Solutions, 5 Waltham St, Artarmon, NSW 2064. Phone (02) 906 6666. 50Hz computer-grade power conditioner For further information, contact Peter C. Lacey Services Pty Ltd, 74 Fulton Rd, Mt Eliza, Vic 3930. Phone (03) 787 2077. Available in models rated from 140VA to 2k VA, the Escort power conditioner range is ideal for electronic equipment requiring well filtered supplies; eg, computer installations. The power conditioners will correct voltage ripples as large as + 15% to - 35% of the nominal POLYSTYRENE CAPACIT RS New range of stylish headphones from Arista Arista has launched a new range of stylish audio headphones that are made in France. Each is terminated in a goldplated 3.5mm stereo plug and all, except the DO-10, come with a 6.3mm stereo plug converter. The DO-10 is priced at $39.95 and would be great for joggers. It consists of two separate earpieces that are simply attached to your ears using covered metal clips. The nominal impedance is 16 ohms, it has a frequency response of 20Hz-20.5kHz and it weighs only 5 grams! The AO-10 is a standard lightweight headphone set that has a comfortable ear cushion for extended listening. The impedance is 38 ohms and it has a frequency response of l8Hz24kHz. The price for the AO-10 is $59.95. The BO-10 is a larger more enclosed version with 107dB sensitivity. The ear cushion covers the ear comfortably and is designed to reduce background noise. Frequency response is Made here in Australia? I to Type? 20Hz-22kHz and the impedance is 38 ohms. This model is priced at $79.95. The top of the range model is the CO-10. It costs $99.95 and has large 44mm diaphragms to cut out all background noise. It has a nominal impedance of 70 ohms and a frequency response of 18Hz-22kHz. All models come in an attractive black and gold finish. For more information, contact Arista Electronics Pty Ltd, PO Box 191, Lidcombe, NSW 2141. Phone (02) 648 3488. New range of miniature relays line voltage to within + 3% to - 6% in only two cycles of the line frequency. Also featured is a noise suppression system for protection against noise disturbances such as lightning. The unit provides up to 120dB of common and 60dB of normal mode noise attenuation. For further information, contact Square D Australia, PO Box 42, Heidelberg, Vic 3084. Phone (03) 480 3511. IRH Components has released new additions to its Fujitsu FBR600 series of miniature PCB mounting relays. The new models feature 16A switching capacity (either 240V AC or 30VDC resistive) in SPST format, have a high contact to coil isolation of 5kV RMS or lOkV impulse, and meet Telecom Australia specifications. Coil dissipation is 0.5W at 20°C for all types, while the coil voltage range covers from 5-60V with 5, 6, 12, 24 and 48V being the preferred types. The operating temperature range is from - 40 tp + 70°C. For further information on the Fujitsu FBR600 series relays contact IRH Components, 32 Parramatta Rd, Lidcombe, NSW 2141. Phone (02) 648 5455. olystryrene Capacitors - 10pF to 1 mF Voltage Range 63VDCW to 10,000 VDCW Tolerance - 0.25% to 10% Allied Capacitors Australia manufactures capacitors to the specification of the customers using high quality, imported polystyrene and aluminium foil with a tolerance of 1 micron. Our capacitors are manufactured to the system of Total Quality Control. We can provide Just In Time delivery if required, together with a Certificate of Conformance if requested. Specific values between 1 0pF and 1 uF are no more expensive than standard value components. You can now design circuits to use a single capacitor rather than a number in parallel or series to achieve a desired value. Personalised labelling is available at no extra cost. Your component code or name can be built into the capacitor. Minimum runs of only 25 allow you to specify a particular value for a prototype run. Delivery lead time for short runs is 3 to 4 working days, and for longer runs is less than 2 weeks. We are also able to produce capacitor styles for applications such as dual mount, end filled and mini style capacitors. Call us now on: (02) 938 4690 ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 JANUARY 1990 95 Floppy price list from Novocastrian The requirements for using the system are an IBM-compatible computer with a hard disc and printer. Initially, you'll have to pay $6.50 to get the discs but that price will be refunded with your first order. For further information, contact Novocastrian Electronic Supplies Pty Ltd, PO Box 87, Broadmeadow, NSW 2292. Phone (049) 62 1358. Temperature- controlled soldering station Novocastrian Electronic Supplies Pty Ltd has announced the release of their "Price List On A Disc". Instead of rummaging through a catalog, users can locate wanted items by using the two-disc system on their computer. Both discs are 5.25-inch 360Kb floppies and contain software to allow the user to search for products, confirm prices and produce an order ready to be faxed or posted back to Novocastrian. ** GREAT VALUE AND TECHNOLOGY ** NEW YEAR SPECIALS ... AT-4000 SYSTEM 12MHz 512K 101KBD 200W PS etc $11 24 .15 VGA MONITOR 0.31 FOR 800x600 $696.00 FOO 1.2Mb 5¼" Japan . $130.00 FOO 1.44Mb 3½" Japan . . $146.25 EC-F/HOO FOO/HOO CONTROLLER 1:1 $169.69 GAL PAL PROGRAMMER - 1 only . $350.00 COMPUTER PRODUCTS . . . ... AT-4000 MOTHERBOARD 12MHz 80286 AT ulg forXT $489.00 ECI VGA-16 EGA, CGA, HGA Modes Card 800x600x16 Res. $399 .00 AT-8000 MB 25MHz 80386 inc 018M 32 bit Mem Exp Board . $2,266. 18 AWARD POST TEST CARD . $802.06 ECIHX CARD FOR XTIAT . $399.00 SAAM Batt Blup Skt - Convert SAAM to NON VOL. . $19.95 2S+P+G $85; FOC $97.25 ; 101 KBD $88 .43; EC-CGMA $99; CASE & 200W PS $207.98; XT/AT CLK $49.95. SAVE 30% ON INDUSTRIAL CONTROL CARDS . . EC111 6511 2MHz SBC with AID DIA Clk Bat . $336 EC109 6809 CPU 2MHz wlClk Bat 2xRS232 Cent 1/F $304 EC545 Colour Crt (RGB) 16k/4 page SAAM 512 Char $238 EC·1F124 INO CONTRLR Forth 10-bit AID, DIA Opto lsol $392 LEDS 3mm & 5mm (Min 100/type) . .. Red $0.04; Red HB $0.07; Green $0.06; Yellow $0.07; Orange $0.07. DIODES (Min 100Nype) ... 1N4001 ; 1N4004; 1N914; 1N4148 . $0.05 QUALITY DISKETTES ... (Pkt of 10, 100% error free , L/time Gltee) 5¼ DSDD . $ 6.29 51/, OSHO . $11.40 311, OSOO . $14.36 3'i2 OSHO . . . . . . $39.00 P&P $8.50 - PRICES INCLUDE SALES TAX 26 Boron St. Sumner Park, Brisbane, Old 407 4. Ph: (07) 376 2955 WELLINGTON NZ: Ph: (04) 85 8742 Fax: (04) 82 8850 96 SILICON CHIP Ken Curry Managing Director spaces on PC boards when an audible indicator is required. The unit (Cat. KPE242) has a continuous tone of 4kHz and can be operated from supply voltages ranging from 3-16V DC. The current consumption is only 7mA but the sound pressure at 30cm is at least 70dB when operated from a 12V supply. For further information, contact IRH Components, 32 Parramatta Rd, Lidcombe, NSW 2141. Phone (02) 648 5455. Keyboard retractor saves space This nicely finished soldering station has five temperature settings from 320°C to 440°C and a LED bargraph indicator which lights when the set temperature has been reached. Rapid temperature compensation is provided by an accurate heat-sensing unit. The chrome plated tip is grounded for safety and is rated at 48W. The power cable is about 1.5 metres in length while the cable from the soldering station to the iron is about 1 metre in length. Priced at $139.95, the Micron temperature-controlled soldering station is available from Altronics Distributors Pty Ltd, 17 4 Roe Street, Perth, WA 6000. Phone (09) 328 2199. World's smallest DC piezo buzzer IRH Components are now stocking what they think is probably the world's smallest DC piezo buzzer. Only 13.8mm in diameter and 7.5mm high, it is perfect for tight If you have to move your keyboard out of the way every time you're not using it, then this device will save you a few hassles. Called the Keyboard Slideaway, the device consists of two brackets which support your computer and its monitor. The keyboard is then securely clamped to the retractable section underneath. It's just the thing if you need the extra desk space. The Keyboard Slideaway is made out of heavy-gauge steel, so it will outlast your computer! It costs $64.95 and is available from Rod Irving Electronics, 48 A'Beckett St, Melbourne; phone (03) 663 6151. You can contact their Sydney store on (02) 519 3134, or call in at 74 Parramatta Rd, Stanmore 2048. Cleaners for records and compact discs tion supplied in a marker pen. This solution is manufactured by Eastman Kodak and will not harm the critical label side of the disc. The Record Cleaner System is a twin brush arrangement that mounts on the turntable centre spindle. It is rotated by hand around the stationary record and employs some 592,000 filaments to remove dust from the record grooves. It also uses a marker pen to apply a cleaning solution and this dissolves and removes oil and static. A stylus brush is also included with the Record Cleaner System and the soiled brushes are easily washed for re-use. The Compact Disc Cleaner costs $29.95 while the Record Cleaner System is $19.95. Both are available from Trackmate Australia Pty Ltd, Suite 1, 1 Johnson Lane, Lane Cove, NSW 2066. Phone (02) 427 3999. Trackmate Pty Ltd has two products that will quickly clean up those dirty CDs and dusty LPs. The Compact Disc Cleaner is designed to clean the disc while it is supported in its storage case. It has 550,000 soft brush filaments which are spring loaded to maintain constant pressure on the disc. The brush itself rotates as the arm is rotated. Washing solution is applied to the disc using a proprietary solu- AUDIO TRANSFORMED cO 6 COLOUR PLOTTERS FUJITSU * Parallel and Serial Interface - GPIB also available * High Quality Resolution 0.025mm * Compact and Lightweight 420 X 260 X 95 mm - 4.5 Kg * Wide Selection of Paper Sizes A3 down to Po stca rd * Wide Applications Business, CAD, Hobbyists etc. FOR PROFESSIONAL, OEM OR AMATEUR Broadca st qualit y auclio transformers ex-stock '-'l o re t han 70 stanclard types avai labl e Fa st prototyping service fo r non-st andard types Comprehensive data ava ila ble on requ est Locally manufactured Compe titi ve ly priced HARBUCH ELECTRONICS PTY LTD 90 Geo rge St . HOR\JSBY \JSW 2077 Phone I 0214 76-5854 FPG316 PAR/SER - $1,299.00 FPG316 GPIB - $1,350.00 +20% Sales Tax. $10 Delivery Pacific Microelectronics Pty.Ltd. Unit A20 / 4 Central Avenue P.O. Box 189 THORNLEIGH N.S.W. 2120 Telephone 02 481 0065 FAX 02 484 4460 JANUARY 1990 97 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Wrong voltages in Studio 200 amplifier I have built a Studio 200 power amplifier, as featured in the February 1988 issue of SILICON CHIP. Why are the voltages that I measured from my module so much different from those on the circuit diagram? Across the two 680 resistors I have measured 0.36V instead of 0.45V as shown, while across the 8.2k0 1W resistor I measured 43V instead of 53V. For the 1000 emitter resistor common to Q4 and Q5, I measured 1V instead of 1.3V. When I tested the module with the two 5600 5W resistors soldered to the fuse holders, I found that Q4, Q5 and Q6 got a bit warm - is that normal or abnormal? Could you advise or explain why the above voltages are different. (L.Y.H., Singapore). How fragile is the intelligent battery charger chip? With reference to the article in the July 89 issue of SILICON CHIP on the Intelligent Charger for 12V gel cells, I would like to inquire what would happen to the UC3906 chip if a load was applied to the output of the charger and the supply voltage (Vin) failed? Would the chip be destroyed? As a matter of interest, connecting the battery incorrectly is disastrous. I know; it happened to me. I enjoy your magazine and hope the articles on Amateur Radio and the Evolution of Electric Railways Continue. (G.C., Ouyen, Vic). • Yeah, well we've found out quite a few more points about this chip since we published our 98 SILICON CHIP • It is apparent from the voltages you have quoted that Q4, Q5 and Q6 are not conducting quite as heavily as they should. In fact, Q4 and Q5 are each pulling about 5 milliamps rather than about 6.5 milliamps each. Q4 and Q5 take their bias from the 2. 2k0 collector resistors associated with the previous stage, Q2 and Q3. The current through this differential pair, in turn, is set by the constant current source consisting of Ql, D1 and D2. If you had measured the voltages around Ql, Q2 and Q3, you would no doubt have found a corresponding reduction in the currents drawn. There are two possible reasons for this. First, your overall supply voltage may be a good deal less than ± 49.5V as shown on the circuit. Second, if that is not the case, the 2700 emitter resistor may be higher that its nominal value or the 56k0 resistor feeding D1 and D2 original article in the July 1989 issue of SILICON CHIP. The chip can be blown both by reverse battery connection and by removal of the input voltage from the circuit. Diodes are needed to protect against these two situations. Second, the circuit we published in the July issue needs finetuning as far as the setting of the trickle charge condition is concerned. As noted previously, we plan to publish at least one and maybe two follow-up articles on this chip - a lot of readers have expressed interest in it. The articles on Amateur Radio will certainly continue but the series on the Evolution of Electric Railways can't go on forever - it will finish in a few months' time. We are glad that so many readers have enjoyed it so thoroughly. may be higher than it should be. Another possibility is that Ql is low in gain or (perish the thought) you have an NPN transistor in there instead of a PNP type. Anyway, you get the picture. The basic clue as to why the voltages aren't quite right will lie around the constant current stage Ql. Mind you, even though the currents aren't quite right, th e amplifier is probably still working pretty close to spec. And when you correct the operating conditions to get the specified voltages, you will find that Q4, Q5 and Q6 will possibly run a little warmer than at present. That's OK. Subaru ignition needs souping up I would like to congratulate you on the excellent articles concerning high-energy ignition in the May and June 1988 issues of SILICON CHIP which I recently obtained through your back issue service. Having decided to improve the ignition on my 1980 Subaru 4WD, I was shocked to discover the prices of imported systems, many of which were of doubtful specification. Turning to the electronic kit market was also somewhat daunting initially until I read the abovementioned articles. However, I still have a problem because the Bosch vane assembly does not fit my vehicle (Hitachi distributor). That leaves the Sparkrite system. Having rung numerous outlets iri Brisbane, I still cannot locate a company marketing this system. Could you give me an address or phone number of a company marketing Sparkrite contactless trigger packs. Furthermore, do you know of anyone who markets inductively suppressed high tension ignition cable in Australia, an aspect not covered by your article. (A.J. , Indooroopilly, Qld). • Unfortunately, you can forget the Sparkrite system. We understand that Sparkrite ignition components are no longer manufactured. That gives you just two options. First, you can try to obtain a solid state ignition system for a later model Subaru from a wrecker's yard, although we think that you will be very lucky to obtain what you want. Second, if that line of enquiry proves unproductive, we suggest you install the High Energy lgntion System as published in the May 1988 issue of SILICON CHIP and use the vehicle's existing points. Admittedly, this will not be quite as maintenance free as a breakerless system but it will give you a worthwhile lift in engine economy and ease of starting. Frustration over mica washers I have nearly completed four SILICON CHIP Studio 200 power amplifier modules but these have ground to a halt because I cannot locate some minor components. (1) T0-126 mica insulating washers for the MJE340, MJE350 and BD139 transistors. These need to be for T0-126 transistors because of their close proximity on the heatsink. Most parts outlets here in New Zealand and Jaycar and Dick Smith Electronics in Sydney offer T0-220 mica washers which are too wide. (2) The 13 x 10mm formers for the output inductors (Jaycar would order the wound chokes in for me at $6.50 each, but they would not ha~e been available before I left Sydney; I will go this way if the formers cannot be located). I hope you can provide some help here because the amps have been nearly ready for the "smoke test" for many weeks now and it is quite frustrating for them to be stalled after so much work and for such simple components! Congratulations on an excellent magazine. It contains the ideal mix of technical articles and constructional projects. (K.M., Silverstream, NZ). • The answer to the problem of mica washers is a nice sharp pair of scissors. Mica washers for 12V power for the LED message board Thank you for your article describing the construction of the LED Message Board back in the March 1989 issue of SILICON CHIP. Now that I have time to go ahead and build it, I would just like to know how feasible it would be to power the board off a 12V car battery, say through the cigarette lighter socket? Any information would be well appreciated. (S.S., Northbridge, NSW) • No problems at all in answering this question. You could certainly run the LED Message Board from a car battery. The T0-126 transistors are hard to get so the solution is to trim down T0-220 washers so that they don't overlap when the transistors are mounted on the heatsink. As far as the chokes are concerned, you don't really need the formers at all although they do add a nice finishing touch. You can wind the chokes without a former - just use a ½inch drill or bolt and wind on the required number of turns in layers. If you are using a ½-inch bolt you can put on a number of washers and a nut to provide temporary cheeks for the choke while it is being wound. Then, when it is wound, take it carefully off the temporary former and dip it in Araldite. When this sets, it will make a selfsupporting choke. Don't forget to thoroughly clean existing bridge rectifier at the input to the power supply will protect the circuit against inadvertent battery reversal. However, we would suggest that you connect a 20V 1W zener diode across the input to the 7805 3-terminal regulator. This will protect the regulator against any spike voltages which may occur at connection or during normal operation of the car's electrical system. You should also fit a fuse to the battery supply line - 2 amps should be adequate. One more point should be noted. The LED Message Board won't work in bright daylight. This was noted in the March 1989 article. and tin the ends of the coil though. At any rate, you don't have to spend $6.50 per coil, do you? Thrown off track by electronic jargon I am just getting started in electronics and on the back page of the November 1989 issue of SILICON CHIP is a Metrix 50 multimeter with a rating of IP66. Could anybody explain what this system is about? (J.B., Townsville, Qld). • This question threw us , too. We contacted the distributors for Metrix meters , Elmeasco Instruments Pty Ltd, and they gave us the answer. IP66 is a stringent European standard for water and dust sealing. Apparently, the Metrix 50 Series multimeters are so well sealed they will float. ~ .,.~~.m:.,~t.:.tt: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP , ETI and EA. L 651 Forest Road , Bexley, NSW 2207. Phone (02) 587 3491. JANUARY 1990 99 Modifying the Studio 200 power amplifier Back in February 1988 we published the Studio 200 power amplifier which has proved to he a very reliable and consistent per£ormer. In the intervening period a number of readers have written to us describing modifications they have made to "audibly improve" the performance. Here are the modifications made by one reader. By LEO SIMPSON Since it was published in February 1988, our Studio 200 power amplifier has proved itself to be very trouble free and many hundreds have been put together without problems. Constructors have been particularly delighted with its very low noise. In that respect it is a lot quieter than many The Studio 200 power amplifier was actually developed from this module which was published in the December 1987 issue. This circuit pioneered the use of PTC thermistors for amplifier and loudspeaker protection. 100 SILICON CHIP commercial power amplifiers, regardless of their cost. But just as there exists a small specialist market for those well heeled people who want commercial amplifiers to sound better, so there is also a temptation among keen audio enthusiasts to modify the Studio 200. Up till now, we have been reluctant to encourage the idea of modifications because of the considerable risk involved. First of all, there is the risk that uninformed modifications may lead to a costly failure in the amplifier. This would be particularly frustrating if the amplifier had performed perfectly up until it was modified. And then there is the risk that the amplifier may sound no better or may sound worse, after the mods have been made. We have also been reluctant to publish readers' modifications to our amplifier designs because, without exception, such modifications have not been accompanied with any analysis or objective measurements to justify the work. This is not to say that the design of Studio 200 is absolutely right in every way. As with any commerical design, the Studio 200 amplifier is a tradeoff between cost and performance. At the time we produced it, we believed the Studio 200 to be a very good compromise. We still do. But ... In publishing the accompanying modifications we are in no way endorsing them. We do not even agree with them. Why then, are we publishing them? To stimulate debate. Here then, is the reader's letter: In relatively recent times I have replaced op amps to gain a small audible improvement in various consumer audio products. I was not happy with the apparent loss of depth information in NE5534 preamps compared to an earlier discrete design I had used, so I built an experimental preamp using an LM394, BC559 and LH0002 buffer in each channel (I believe in low output impedance). I repeatedly became aware of a phenomenon whereby after a certain amount of time I realised that the soundstage had considerably improved and the sound was ,--_ _ _ _ _ _____ _ _ _ _ __ _ _ __ _ _ _ _ ____,.,__ _ _ _ __ _ _ _ _ _ _ _ v+ 5A r lN;:_..s 22k 1'/, 22k 1% OUTPUT .,. -;- * 04 47k 1% 2xBF469 2.2k 1% 2.2k 1% 5A 100() 1°/, ,..___ _ _ _ _ _ _ _ ____,.,__ _ _ _ _ _....,_ _ _ _ _+ - - ---<11-- - - -- ..--------------v+ ......----v- 0.1+ RIGHT 0.22 * HFE MATCHED TO 10% 240VAC 0.22 10k 1W V- RIGHT N V+ LEFT 0.22 10k 1W 0.22 10k 1W . V- LEFT Fig.1: the modified circuit of the Studio 200 amplifier uses current sources for the second differential pair instead of the now tried and proven current mirror arrangement which is very common in op amp ICs. Note that quite a few more components are employed and that the amplifier has a gain of 23 down to DC. "sweeter". Each time I noticed the change, I read all DC voltages and on every occasion, the potential difference between the collectors of the input differential pair was less than 5mV! Unfortunately the improvement slowly disappeared (dependent on the surrounding temperature or ventilation of the preamplifier). Several versions of the preamp later on, the BC559 was replaced with an imported 2N3811A dual transistor (at greater than $20 each) and the LH0002 with a discrete version using selected BC559 and BC549 transistors. The unused half of the 2N3811A was given an identical collector load to the other half and its collector voltage used to control a shunt tr ansistor across the reference LED of the adjustable input pair current source to maintain optimum conditions. This arrangement also resulted in ± 5mV offset from the DC coupled preamplifier. I fluked obtaining a beautiful dual 18-position rotary switch in a Jaycar switch pack and fitted 1 % metal film resistors to it, to make a precision matched dual volume control. Surprisingly, the sound was less harsh also. More recently, I decided to try similar circuitry in a 100 watt/ channel amplifier based on the Studio 200. The amplifier (as it now stands) is not suitable for the average home constructor as it requires some parts selection and the dual PNP input transistor. A competent designer could overcome most of the drawbacks however. The audible effect of the input pair collectors being adjusted to less than 5mV difference is at least as audible as in the preamplifier and the amplifier audibly outperformed my reference " Tillbrook 6000" which uses matched pairs throughout, 1 % resistors and polystyrene capacitors in lieu of ceramics wherever possible. The JANUARY19 90 101 +4!1.5V t 01 1N4002 2700 02 1N4002 f 48.1V 0.5V :_J B 01 BC556 C ~ .,. 18k 33.3V et,. 07 B0139 .012 --1 B l 06 BF470 C 5A 0.1i B E 0.1 INPUT 22k B 1k ... VR1 5000 47 6VW:r .,. 04 B l ! 2xBF469 C B 48.3V 2.2k ~ :-i --1 :__J 1.9V 2.2k 1.9V -49 .5V O.llSTUDIO 200 STEREO POWER AMPLIFIER SC1-1-288 Fig.2: this is the circuit of the Studio 200 as originally published in the February 1988 issue of SILICON CHIP, although minus the power supply. Its signal to noise ratio was close to - 120dB with respect to full power. That's very quiet. equipment used for auditioning was a much modified Marantz CD65 player, the previously mentioned preamplifier and B&W 801s in an almost ideal listening room. I am not sure what the improvement is caused by, as I expect the distortion would already be vanishingly low. Perhaps supply rejection is the answer? I feel that this phenomenon is worthy of further investigation, particularly as most designers do not fully take into account the loading effect of the succeeding base emitter junctions across the collector resistors of the input pair. The loading transistors must track each other thermally if the input pair is not to be unbalanced. Alternatively, if only half the input pair is loaded, an appropriate value resistor should be fitted to the collector of the other input transistor. Food for thought? (A.K., Chatswood, NSW). Potential problems Readers should compare the accompanying circuit diagram (Fig.1) with that for the Studio 200 (Fig.2) - see also SILICON CHIP, February 1988 - to see how extensive the modifications are. We do not propose to analyse the effect of these modifications as we would prefer Notice to Subscribers Are you about to change your address? Please advise us by the middle of the month by filling in the form on your address label and posting (or faxing) it to us. If you have any queries about your subscription, call us or write to us at: SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. Telephone (02) 982 3935. Fax (02) 982 9553. 102 SILICON CHIP readers to make comments. Briefly though, we see a number of potential problems in the modifications. First, the use of separate bridge rectifiers and filter capacitors for each channel, while superficially an advantage from the point of view of better channel separation, may cause circulating currents in the earth returns. This could well lead to audible distortion or low frequency instability. Second, we can't see how the use of a LED (light emitting diode) will lead to improved power supply rejection. At a current of 2mA, a LED will typically have around the same dynamic resistance as a 1N4002 power diode which was originally specified for the Studio 200. In fact, at 2 milliamps, the dynamic resistance of 1N914 or 1N4148 small signal diodes is a good deal better. There are many other ramifications of the proposed modifications. For the time being we will not comment on these. We invite readers to have their say. ~ CEN'l Cash in your surplus gear. Advertise it here in Silicon Chip. MEMORY CHIPS CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale . If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS PRICES JANUARY 1990 or SIPPS DIP ZIP 2 4 3 5 9 x 1MbLP 9 x 1Mb HP IBM 9x1MBLPIBM 8 x 1Mb LP 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9.00) 21 ($9.40) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11.00) 26 ($11.40) 27 ($11.80) 28 ($12.20) 29 ($12.60) 30 ($1300) Name ..... .... ..... .. .... .... ..... ....... . ··•· ··· ······· ·· ·· ····· ·•··••· · ······ ·· ·.. , - , ,- , . , .. ... Street Postcode Suburb/Town Enclosed is my cheque or money order for$ .. Bankcard D Visa Card D MasterCard . .. . or please debit my D Card No __,__--"'------_L_-'---'----'-- '---1 -'--~-'-__,__--"'------_L_-'---'--- - ' - ~ Signature ..... ............... .... ........ . . . ..... ..... ... ..... Card expiry date ....... / ...... ./ .. . FOR SALE WOW! DRAM PRICES have dropped. Now is the right time to build your own FIX-A-KIT $15 PER HOUR LABOUR NO CHARGE FOR KITS THAT CAN'T BE REPAIRED 3 MONTHS WARRANTY ON REPAIRS CONSTRUCTION .AVAILABLE HYCAL INSTRUMENTS DESIGN, MANUFACTURE, REPAIR OF ELECTRONIC EQUIPMENT (02) 633 5897 parallel printer buffer. Advertised since January 1985 . Featured in AEM in January 1987 and SILICON CHIP in October 1989. Over 2500 units sold. Same kit, just updated. Now 8K-1 M. No obligation. For a free catalog send a 41 c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. PUBLIC DOMAIN & shareware software for IBM & compatibles . Catalog disc $4.00 . Also TV-REPAIR.TXT which covers faults in most popular brands. It can save hours of work. On a 5 ¼-inch disc. Just $28.00 inc. p/post. Martins Television Service, PO Box 1013, Taree, NSW 2430. 156.00 185.00 210.00 149.00 411000 (1 Mb) 414256 (1 Mb) 41256 41464 (256) 4164 2.50 15.00 16.00 4.25 4.60 2.80 41256 411000 (1 Mb) 4.00 18.00 5.00 20.00 Sales tax 20% 6 Speed 120ns 100ns sons Prices (excluding tax) 38.00 42.00 50.00 Chip type SIMMS 9 x 256 3.70 168.00 250.00 160.00 15.80 17.00 4.90 5.00 Overnight delivery Credit cards welcome DISCOUNTS FOR DEALERS PELHAM Tel (02) 427 0011 Fax (02) 428 5460 FUJITSU MEMORY DRAM DIP 256K x 1 1OOns DIP 256K x 4 8Dns . . . ZIP 256K x 4 8Dns. .. DIP 1 MB x 1 sons . ... . .. ZIP 1 MB x 1 sons . . .. . SRAM DIP BK x 8 1OOns DIP 32K x 8 1OOns DRAM CONTROLLER MB1430/1 P $3.95 $16.00 $16.50 $15.00 $15.50 $ 4.50 $12.00 $15.50 PACIFIC MICROELECTRONICS PHONE (02) 481 0065 FAX (02) 484 4460 Add Sales Tax 20 % COMPONENTS: 256K 1 20ns DRAM $10; 64K 150ns $4.86. 27128 EPROM $9.50; 27256 $11; 27512 $19. Also TTL, linear, diodes, transistors. Send SSAE to Enersun Electronics, 34 Orangedale Rd , Lesmurdie, WA 6076 . Phone (09) 291 8678. SATFAX: WEATHER SATELLITE picture receiving program for IBM XT/AT. Displays in 64 colours. Needs EGA colour monitor & card, AM demodulator & ADC interface. $45 plus $3 postage . RADFAX2: HF WEATHER FAX, Morse & RTTY receiving program for IBM XT/AT . Needs CGA, SSB HF, FSK/tone JANUARY 1990 103 r~---------------------i FREEPOST SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139 Collaroy Beach, NSW 2097, Australia. NO POST AGE STAMP REQUIRED IN AUSTRALIA. 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IFC Dauner Electronics ... .... ..... .. 1 7 David Reid Electronics ......... 8 ,9 Dick Smith Electronics ..... 36-4 1 Electronic Solutions ....... . 24,25 Energy Control ..... ...... ........ . 96 Geoff Wood Electronics ........ 13 Harbuch Electronics ........ 91,97 HycaJ Instruments ...... ........ 103 Jaycar Electronics ..... .. ... 49-56 Lawson Radio . . . . . . . . . .. . . .. .. .. . . 1 7 Pacific Microelectronics . 9 7, 1 03 PC Marketplace ... ... ..... ... 68-69 Pelham ... ........... .. .... ......... 103 RCS Radio .. ................... .. ... 99 Rod Irving Electronics ... .. 92,93 Silicon Chip Binders .. ....... . OBC Trackmate Australia ...... .. ........ 3 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • ACS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Jemal Products, 5 Forge St, Welshpool , WA 6106. Phone (09) 350 5555 . • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. 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